Book Review of The Defining Decade: Why Your Twenties Matter — And How to Make the Most of Them Now by Meg Jay

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This Book Review of The Defining Decade: Why Your Twenties Matter — And How to Make the Most of Them Now by Meg Jay is brought to you from Omar Garza from the Titans of Investing.

Genre: Popular Developmental Psychology
Author: Meg Jay
Title: The Defining Decade: Why Your Twenties Matter — And How to Make the Most of Them Now (Buy the Book)


Meg Jay’s book, The Defining Decade, advises young adults everywhere how to tackle most of the difficult issues they will face in their twenties. The book introduces three major topics: Work, Love, and the Brain and the Body. Using these three topics, The Defining Decade illustrates a refreshing take on the importance of one’s twenties.

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The first major topic discussed is work. During this part of the book, Meg tackles the common misconception of thinking that the twenties are simply the best years of one’s life.

She shows that for many young adults, the twenties can be some of the most uncertain and difficult years of life. This is due to the underemployment effect, which is experienced when a person is overqualified and does not learn anything of worth in certain jobs.

The result is a feeling that one’s career has already slumped, despite its recent beginning. In addition, the lack of direction, guidance, and knowledge that many young adults possess further compounds this uncertainty.

The Work section places strong emphasis on the value of identity capital – the collection of an individual’s personal assets. Meg summarizes identity capital as what one brings to the table and then demonstrates how it is crucial for and individual’s work life. Furthermore, the worth of weak ties, such as acquaintances, and the multiple benefits they bring to the workplace are introduced.

In the second section of the book, entitled Love, relationships are analyzed and the importance of choosing an adequate partner is discussed. During this time in life, individuals have the opportunity to select their family.

Young adults or “twentysomethings,” as Meg Jay calls them, must determine what types of relationships they want to have in life in order to proactively search for possible partners. This section also warns “twentysomethings” about the cohabitation effect and demonstrates how it can be toxic to relationships.

The cohabitation effect occurs when couples live together before marriage or before establishing a strong sense of commitment. Furthermore, it discusses the importance of valuing yourself and making sure chosen partners value who you are as well.

She concludes that people in their twenties determine many aspects of life during this decade, but none are more important than determining who they marry. The final section of the book examines the Brain and the Body. Here, Meg emphasizes the growth of the “twentysomething” brain.

As the brain enters its final stages of development, the frontal lobe of the brain finishes maturing. The frontal lobe is where judgment and reason reside, which means that it helps us deal with uncertainty. Apart from the development of the brain’s frontal lobe, confidence, which is obtained through experience, is also gained in our twenties.

After analyzing confidence, Meg coins the term “getting along and getting ahead” by discussing the importance of investing in adulthood. Finally, the topic of fertility management is covered, providing valuable information for those who wish to have a family in the future.

Section I: Work

The “twenties” decade impacts an individual’s work life more than any other. This is the opportune time for a young adult to move forward. One of the most important parameters determined in this decade is identity capital. As Erik Erikson, a famous German psychoanalyst, states that “everyone should create his or her own life.” A period of personal walkabout, or Wanderschaft, is important in determining one’s own identity.

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Identity capital is our collection of personal assets.

Our personal assets represent the individual resources we have acquired over time, as well as the investments we have made in ourselves. Meg Jay states that these are the things we do well enough, or long enough, that they become a part of who we are. Identity capital is how we build ourselves over time. Thus, identity capital is what we bring to the marketplace.

Meg advises young adults, or “twentysomethings,” as she calls them, to always take the job with most identity capital. Many young adults do the opposite and therefore experience the problem of underemployment.

Underemployment occurs when an individual is overqualified for a job and does not feel challenged, an unfortunate situation that both hinders the development of important skills and creates boredom amongst employees.

“Twentysomethings” rely heavily on their so-called urban tribe.

The urban tribe represents a close group of friends with whom many fun experiences are shared. This is the ‘family away from home’ that is portrayed in many TV shows and movies. According to The Defining Decade, the urban tribe is overrated.

With so much attention being paid to the urban tribe, many young adults limit their social lives by acquainting themselves with like-minded peers. In the long run, the urban tribe helps us survive, but it does not help us thrive.

Meg refers to a term called the ‘Benjamin Franklin Effect’ when dealing with weak ties.

The strength of weak ties is a sociological theory which states that acquaintances are more likely to provide help in a work-related matter than those who are close to us. As a state-level politician, Benjamin Franklin wanted to win over a fellow legislator.

Benjamin Franklin learned that the legislator owned a library, which included “a very scarce and curious book.” Benjamin expressed his interest in borrowing the book, which the legislator agreed to. A week later, Benjamin returned the book with a note strongly expressing “his sense of favour.” At the next meeting in the House, the legislator spoke to Benjamin with great civility and soon they became good friends.

From this past experience, the Benjamin Effect was created. If weak ties do favors for us, they will be more prone to liking us. Subsequently, they will become more likely to do additional favors for us in the future.

The Ben Franklin effect shows that, while attitudes influence behavior, behavior can also shape attitudes. This means that when we do a favor for someone, we come to believe that we like that person. Many people remember starting their first jobs themselves, which means there is a special sentiment felt towards “twentysomethings.”

People work to achieve their full potential. Many young adults feel the urge to achieve their potentials at an early age without realizing that it usually happens in one’s later years. They live according to the “shoulds” or “supposed to’s” when they should be living by their own set of goals.

Many young adults feel as if they should be living their professional and personal lives in a certain predetermined way, formed by the environment around them. Meg states that goals direct us from the inside, but the “shoulds” are paralyzing judgments from the outside.

When liberated from the judgment of the “shoulds”, one can realize what is important and can begin focusing on the future. In the end, it is important to remember that one’s twenties are more about potential than proof.

Conclusively, Meg conceptualizes the idea that building a customized life is completely up to the individual. The options are out there, but it is up to the person to gather himself and to seek out what he wants. In the end, claiming a career or getting a good job is not the end; it is the beginning.

Section II: Love

David Brooks, a political and cultural commentator, once said, “The most important decision any of us make is whom we marry.” Within one decision, you choose your partner for virtually everything else in life. Almost every aspect of your life will be intertwined with those of your partner.

Many popular magazines and TV shows depict a “twentysomething” culture dominated by singles that avoid commitment.

Behind closed doors Meg hears a different story. She states that she has yet to meet a young adult who does not want to get married or at least be in a committed relationship. Many “twentysomethings” feel timid about expressing their actual feelings regarding relationships and marriage.

Many of them also live under the common misconception that relationships are something completely out of their control. It is never too early to begin thinking about and working on relationships. Doing so could aid in producing meaningful and happy marriages.

Young adults feel the necessity to be single throughout their twenties and to focus on marriage at a later time.

Meg states, “doing something later is not necessarily the same as doing something better.” As the average age of marriage rises, the divorce rate holds steady at about 40 percent, meaning that later marriages have problems of their own.

Instead of growing together in their “twentysomething” years, many couples that marry older are set in their ways. Past destructive relationships can diminish faith in love. An additional consideration of waiting, is the continually shrinking pool of singles, which becomes becomes smaller and more selective on an ongoing basis.

Many of Meg’s clients do not take relationships seriously or don’t think they are allowed to. At the same time, many of them fear the ‘Age Thirty Deadline’, wherein the common saying is, “I better not be alone when I’m thirty.”

Although young adults feel like it is too early to take their relationships seriously, as soon as they turn thirty, relationships seem to be a pressing matter. The twenties should not be spent settling for low-criteria relationships that have no hope or intention of succeeding.

Meg remembers what one of her first bosses told her about a “twentysomething” client named Alex: “The best time to work on Alex’s marriage is before she has one.”

By partnering with another person, an individual gets both an opportunity to join a second family, and start his own. These are the families that life will be about, which will define the decades to come. As Anthony Brandt once said, “Other things may change us, but we start and end with family.”

Young adults have a common misperception that living together will be an adequate test for marriage.

Statistics have shown that couples that live together before marriage are less satisfied with their marriages and more susceptible to divorce. Sociologists call this the ‘Cohabitation Effect’.

The Cohabitation Effect can be devastating because many decisions tend to “slide” instead of being made. The idea is that after dating for a while, couples begin to sleep over frequently. This occurrence continues, and soon thereafter the couple is living together.

No decision or thought goes into living together; rather, it just happened. “Twentysomethings” must learn to be intentional with their decisions and reasons behind living with a partner.

Besides the “slide” concept, there are two additional reasons why cohabitation proves to be toxic for relationships. These are known as the “lock in” and “switching costs” concepts. The “lock in” concept explains that it is difficult for people to get out of cohabitation.

It also decreases the chances of someone searching for other options once an investment in something has been made. Switching costs represent the efforts required for someone to make a change. The greater the investment made or the switching costs are, the more likely that a person will not be willing to make any changes.

This can be dangerous for “twentysomethings” since they might remain in a particular relationship based on the strenuous efforts it would take to make a change.

In contrast, couples that are engaged and decide to live together before their marriage do not suffer from the cohabitation effect.

This occurs because the couple has made a clear public commitment and has shown their intent for each other. It is the couples that live together before being clearly and mutually committed to one another who suffer from poor communication, low levels of commitment, cohabitation effect, and marital instability.

Another problem young adults face in their relationships involves ‘dating down’, which has nothing to do with looks. It involves partners taking each other seriously instead of dating ‘down’ to old, low, or inaccurate versions of each other.

“Twentysomethings” who ‘date down’ usually tend to have untold stories.

Most of the time, these untold stories go back to high school or college. During high school or college, young adults begin learning who they really are and why we are that way. If someone had a difficult and cruel experience in high school, he or she could be more vulnerable to making bad relationship decisions later in life.

Fortunately, these experiences can be changed through conversations and new experiences. It is up to the individual to understand what happened, move on, create new experiences, and decide to form intentional relationships that can prosper.

When it comes to relationships, compatibility is important. Meg states that in order for relationships to succeed, both partners need to be “in like”. Being “in like” means being similar in ways that matter and genuinely liking who the other person is.

The more similar people are, the more they are able to understand each other. Many people only think of what it is that they want from a partner, but this only leads to realizing what the deal-breaker characteristics are. In comparison, the “who you are” questions are more important.

These questions determine an individual’s personality. As a result, when the personalities of two people are similar, the chances of a couple’s relationship of being happy are higher.

Married couples tend to be the least alike when it comes to each members’ personality, because personality is less obvious and not as easy to recognize. In order to judge the personality of an individual, Meg introduces “The Big Five Model”.

The model includes: Openness, Conscientiousness, Extraversion, Agreeableness, and Neuroticism. The model focuses on who you are and how you live, rather than what you like. It determines anyone’s personality and helps decide whether a particular person has a similar personality to another.

Section III: The Brain and the Body

Phineas Gage was a 25-year-old railway worker back in 1848. At his job, Gage drilled holes in rock, filled them with gunpowder and sand, and then packed them down with a tamping iron.

One day, Gage had an unfortunate accident and a rod entered his head under the left cheekbone. This metal rod passed behind his eye socket and exited through the top of his skull. Amazingly, Gage could still talk and communicate with the people around him after the accident.

As months passed, close friends and family began to realize that Gage was no longer himself. His behavior was different and erratic. His doctor determined that, “the balance between his intellectual faculties and animalistic propensities seems to have been destroyed.”

Gage was no longer himself and his condition implied that although the forward part of the brain may not have much to do with whether we live and breathe, it has a lot to do with how we act.

The human brain develops from bottom to top and from back to front.

The oldest part of the brain, which is present in our ancestors, controls our breathing, senses, emotions, sex, pleasure, sleep, hunger, and thirst. The forward part of the brain, especially the “frontal lobe,” is the most recent part of the brain that has developed for humans through evolution.

This frontal lobe is also the final area to mature for each person and is nicknamed “the seat of civilization”. In this area of the brain reason and judgment reside. This front area of the brain processes probability and time thus it is where we tackle uncertainty.

The frontal lobe of the brain does not fully mature until the late twenties.

Prior to this time, the emotional brain is fully functional while the forward-thinking frontal lobe is still a work-in-progress. Since the frontal lobe is still developing, many young adults behave “unevenly.”

Meg presents that many “twentysomethings” are confused about the fact that they went to good colleges and obtained astounding grades, but don’t know how to start their careers, who they should date, or why they cannot calm themselves down at work.

Being smart in school is about how well you solve problems that have correct answers within a set time limit. Being a forward-thinking adult is about how you think and act, especially in uncertain situations. The frontal lobe is where adults move beyond the fruitless search for a black-and-white answer and learn to tolerate better shades of gray.

In reality, forward thinking doesn’t just come with age, but rather it comes with practice and experience. There is no better time to learn and strengthen the frontal lobe of the brain than during our twenties, when the brain is primed for it.

People are more likely to remember highly emotional events, such as times when they were happy, sad, or embarrassed.

Because our twenties are when we transition into new experiences, “twentysomething” life is full of new and surprising moments. This can be proven by many studies showing that more vivid memories come from early adulthood than any other developmental stage.

Indeed, some memories are remarkably happy, such as getting a dream job, while others can be especially sad or difficult, such as hitting “Reply All” on an email intended for one person. Everyone learns the hard way at one time or another, and it is a jarring but efficient way to grow.

When young adults enter the workforce, attaining a job that is neither easy nor safe, they are shocked.

They find themselves at the absolute bottom. From a dissimilar perspective with similar issues, managers usually have positions of power because of their talent or experience rather than their managerial skills or GPAs. Some of these bosses are not interested in being mentors and others don’t know how. In addition, these are the people who are often tasked with teaching young adults how to navigate the workforce.

During their work experiences, “twentysomethings” take difficult moments exceptionally poorly. Compared to older adults, they find negative news more memorable than positive news. Young adults generally feel anxious and angry when their competence is criticized.

By contrast, experienced adults generally take bad moments less seriously and give these moments less importance. As William James, the father of U.S. research psychology, once said, “The art of being wise is knowing what to overlook.” Having the ability of knowing what to overlook is one possession that older adults have that younger adults lack.

With age comes a positivity effect because older adults typically focus more on positive occurrences and disengage personal conflicts. As people age, they feel less like leaves being blown by the wind but more like trees.

Many young professionals feel second-rate and unconfident at their jobs.

Some have the idea that many people are innately confident at their work. This outlook on things is portrays a fixed mindset. A fixed mindset is a way of thinking in black and white. When it comes to confidence, some people think that there are haves and have- nots.

On the contrary, a person with a growth mindset believes that people can change and that success is something to be achieved. For those people who have a growth mindset, failures may sting but they are also viewed as opportunities for improvement and change.

Research has shown that students with growth mindsets perform better overall in school and report feeling confident, enthusiastic, and strong once it is time to graduate. Having a fixed mindset inhibits success.

As shown, confidence doesn’t come from the inside out but rather it moves from the outside in. Fake confidence comes from stuffing out self-doubt and empty confidence comes from parental platitudes.

Real confidence comes from mastery experiences, which are actual moments of successes, especially when things appeared difficult.

Whether it comes to love or work, the confidence that overrides insecurity comes from experience. This confidence means trusting yourself that you will get the job done.

Young adults who hide out in underemployment (especially those who are hiding because of a lack of confidence) are not helping themselves. Experiences are the only way for someone to gain true confidence. Subsequently, for work success to lead to confidence, the job has to be challenging and it must require effort.

The job must also be done without a great degree of help and it cannot go well every single day. A long run of easy successes creates a fragile confidence that can be shattered when the first failure comes along.

A resilient confidence comes from succeeding and from surviving failures. Every experience counts, so the more valuable and challenging experiences you have, the closer you are to obtaining the so-called ‘10,000 hour mark’ of true mastery and confidence.

Ultimately, as Dale Carnegie said, “Inaction breeds fear and doubt. Action breeds confidence and courage. If you want to conquer fear, do not sit home and think about it. Go out and get busy.”

During the decade of the twenties, personalities change more than at any other time. This is confusing for many because conventional wisdom tells us that childhood and adolescence is when our personalities transform the most.

The twenties are a time when people and personalities are poised for transformation. Since the twenties are when many individual renovations happen, it is important that life be taken seriously.

In our twenties, positive personality changes come from what researchers call “getting along and getting ahead.” Feeling better does not come from avoiding adulthood, rather it comes from investing in it. These investments made in work and love drive personality changes.

For those who do not invest in themselves, they feel as if they are not getting along or getting ahead, which makes them feel angry and alienated. Also, “twentysomething’s” well-being is fostered through committed relationships. In our twenties, we feel more secure and responsible when we are in stable relationships.

Relationships help reduce social anxiety and improve interpersonal skills. As we take part in partnering, we find ways to feel more competent in the adult world.

Numerous studies from across the globe show that life starts to feel better across the “twentysomething” years. This occurs because we become more emotionally stable and less tossed around by the high and low points in our lives.

We become more conscientious and responsible, and as a result, we become happier and more confident. With this confidence, we are able to set goals and work towards them, which also helps structure our future years.

Meg states that goals have also been called the building blocks of adult personality. Who you will be later in life is being built out of the goals you are setting for yourself today.

When to start a family is an important goal that people sometimes forget about.

Germaine Greer, a feminist theorist, makes the valid point that the management of fertility is one of the most important functions of adulthood. As average life expectancy increases and adults marry at an older age, more couples are having children in their thirties and forties; this means that there are more educated moms in society, which is good for children.

Another implication is that women now outnumber men in the workplace, meaning that women, in addition to men, must balance work and family. Regardless of this change, our bodies function in a way that dealing with infertility has become a modern day issue.

Most young adults have goals of raising children and having happy families.

Those in their twenties have the right to know that the years ahead are the most fertile. Fertility peaks for women during the late “twentysomething” years. There is a decline at ages thirty and thirty-five with a steep plummet at age forty.

Egg quality decreases and the endocrine system, which controls women’s hormones and tells the body how to proceed with pregnancy, becomes less effective. On the other hand, men produce less fertile sperm as they get older. Older sperm may be associated with various neurocognitive problems in children such as autism, schizophrenia, and dyslexia.

If fertility intervention is needed, it costs around $25,000 for a couple in their twenties and it costs around $35,000 for a couple in their thirties. At age forty the treatment costs about $100,000 and at age forty-two it triples to $300,000.

All things considered, it is important to keep in mind when to have children. Couples that do not plan ahead suffer through multiple rounds of fertility treatments, shrouded marriage pregnancy, and even babyhood anxiety or stress.

Young adults also have a common problem known as present bias.

Present bias happens to people of all ages who discount the future, favoring the rewards of today over the rewards of tomorrow. Simply put, most people would rather have $100 today than $150 tomorrow. Young adults in their twenties are especially prone to present bias.

This is because their brains are still developing the forward thinking required to anticipate consequences and plan for the future. Present bias occurs often when young adults live under enthusiastic clichés such as “you’re only young once” or “have fun while you can.”

These phrases encourage us to take risks and live under the “now-or-never behavior.” This “now-or-never behavior” does not actually make anyone happy for long, and it includes: partying, having sex with multiple partners, blowing off responsibilities, being lazy, and not having a real job.

This lifestyle makes living in the present easy, and planning for the future very difficult. Present bias is especially strong in “twentysomethings” who put a lot of psychological distance between now and later. Love and work appear to be far off into the future. The problem with feeling distant is that it leads to abstraction and subsequently abstraction leads to distance; a vicious cycle can quickly form.

The further away love and work seem, the less we need to think about them; the less we think about them, the further away it may feel. Meg encourages young adults in their twenties to sketch out a timeline aligned with their personal and professional goals. For in the end, as Meg states, there is a big difference between having a life in your thirties and starting a life in your thirties. would like to thank the Titans of Investing for allowing us to publish this content. Titans is a student organization founded by Britt Harris. Learn more about the organization and the man behind it by clicking either of these links.

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