The Defining Decade by Meg Jay

The Defining Decade by Meg Jay

The Defining Decade summary

Many say “thirty-is-the-new-twenty” as if our twenties don’t matter. Our twenties set the stage for adulthood that's either prosperous and fulfilling or not. The Defining Decade explores career, love, and children and helps twentysomethings invest in their lives now rather than suffering underemployment, divorce, and childlessness later.

The Defining Decade notes & quotes

Here are my notes and quotes on The Defining Decade by Meg Jay. My notes are casual and include what I believe are the essential concepts, ideas, and insights from the book, along with direct quotes from the author.

Introduction: Real Time

  • “The unloved life is not worth examining.” — Sheldon Kopp
  • “Uncertainty makes people anxious, and distraction is the twenty-first century opiate of the masses.”


Identity Capital

  • “Identity capital is our collection of personal assets. It is the repertoire of individual resources that we assemble over time.”
  • When people don’t build career capital in their twenties, they are headed for a lifetime of unhappiness and underemployment.
  • “The longer we take to get our footing in work, the more likely we are to become, as one journalist put it, “different and damaged.”
  • “Twentysomething unemployment is associated with heavy drinking and depression in middle age even after becoming regularly employed.”
  • Economists and sociologists agree twentysomething work has a disproportionate impact on career outcomes.
  • About two-thirds of lifetime wage growth occurs in the first decade of our careers.
  • Data from the U.S. Census Bureau shows that salaries generally peak in our forties.
  • Twentysomethings should take the job with the most capital.
  • “You can’t think your way through life.” said one patient. “The only way to figure out what to do is to do—something.

Weak Ties

  • An urban tribe may help us survive but does not help us thrive.
  • “Similarity breeds connection,” but people like us don’t expose us to new people, ideas, and opportunities.
  • Weak ties, however, give us access to something fresh. Weak ties are people we are loosely connected with.
  • When weak ties do us a favor, they begin to like us.
  • Attitudes affect behavior, but behavior also shapes attitude.
  • Numerous studies show altruism is linked to health, happiness, and longevity—“as long as the help we give is not a burden.”
  • When you ask weak ties for something, some will say no, but more than you think will say yes.

The Unthought Known

  • Many twentysomethings feel overwhelmed knowing that they can do anything.
  • Acknowledging “My life is up to me” can be terrifying.
  • “Being confused about choices is nothing more than hoping that maybe there is a way to get through life without taking charge.”
  • Sometimes when we don’t make a choice, we avoid what we know.
  • The real question is, “What would you do if you didn’t win the lottery?”
  • What could you do well enough to support the life you want that you won’t mind doing in one form or another for years to come?
  • “Unthought knowns are those things we know about ourselves but forgot somehow.”
  • Fundamental uncertainty comes from choosing something we want but not knowing how to get it.
  • “It is working toward something even though there is no sure thing. When we make choices, we open ourselves up to hard work and failure and heartbreak, so sometimes it feels easier not to know, not to choose, and not to do.”
  • “Not making choices isn’t safe. The consequences are just further away in time, like in your thirties or forties.”
  • The “tyranny of the should”—what others want for us—is about glory and keeps us from doing what we’re meant to do.
  • The tyranny of the should pits us against our own best interests.
  • “Facebook is less about looking up friends than it is about looking at friends. Rather than a way of catching up, Facebook can be one more way of keeping up.”
  • Each of us has an intrinsic urge to grow into our potential, similar to an acorn.
    Some dream too big, others too small.

The Customized Life

  • Setting boundaries helps us understand who we are.
  • Identity and career cannot be built around what you don’t want. It’s vital to shift from a negative identity, what you are not, to a positive one, what you are.
  • “Being against something is easy.” Being for something is hard.
  • When your career experience is limited, having a good story about who you are and what you want will help you leap over those who don’t.
  • The first step to a good story is claiming our interests and talents and crafting a narrative around them. Your goal is to balance complexity with cohesion.
  • Schools and companies want communication and reasoning more than originality and creativity.
  • “Interviewers want to hear a reasonable story about the past, present, and future.
  • How does what you did before relate to what you want to do now, and how might that get you to what you want to do next?”
  • “Life does not need to be linear, but it does need to make sense.”


An Upmarket Conversation

  • “I have yet to meet a twentysomething who doesn’t want to get married or at least find a committed relationship.”
  • Statistically, postponing marriage, in and of itself, does not increase the odds of staying together.
  • “In the world of mental health, the lowest-functioning clients and the highest-functioning clients receive the worst care.”
  • “Resilient people are usually very likable.”
  • Of the clients with the most challenging childhoods know the least about getting what they want in love yet need a good partner the most.
  • “When you partner with someone, you have a second chance at a family.”

The Cohabitation Effect

  • There’s a saying in psychotherapy, “the slower you go, the faster you get there.”
  • “Couples who ‘live together first’ are actually less satisfied with their marriages and more likely to divorce than couples who do not. Sociologists call this the cohabitation effect.”
  • Fifty percent of twentysomethings will live with their partner during their twenties.
    Once you live with someone, it isn’t easy to get out.

On Dating Down

  • “The most difficult thing to cure is the patient’s attempt at self-cure.” - Masud Khan
  • Sex makes us feel special, wanted, and validated.
  • “If I don’t find someone,” lamented one client, “I view it as being rejected by everyone.”
  • Our twenties carry our most self-defining experiences and memories.
  • Stories we leave untold are often about shame, yet these stories have the most significant potential for change.
  • Life stories of ruin can trap us. Life stories about triumph can transform us.

Being in Like

  • “In like” means “being alike in ways that matter and genuinely liking who the other person is.”
  • “Studies show couples who are similar in terms of socioeconomic status, education, age, ethnicity, religion, attractiveness, attitudes, values, and intelligence are more likely to be satisfied and less likely to seek divorce.”
  • Bust, these are dealbreakers, not matchmakers.
  • People with similar personalities are more likely to be satisfied.
  • “Personality is not about what we have done or even about what we like. It [personality] is about how we are in the world, and this infuses everything we do.”
  • The Big Five personality model—Openness, Conscientiousness, Extraversion,
  • Agreeableness, Neuroticism—is about who you are and how you live.
  • “Personality remains relatively stable over time.”
  • More couples split not because things change but because things don’t change.
  • “Neuroticism, or the tendency to be anxious, stressed, critical, and moody, is far more predictive of relationship unhappiness and dissolution than is personality dissimilarity.”

The Brain and the Body
Forward Thinking

  • The oldest parts of the brain control breathing senses, emotions, sex, pleasure, sleep, hunger, and thirst, or the “animal propensities.”
  • The frontal lobe is the seat of reason and judgment, where rational thoughts balance and regulate the emotional brain's feelings and impulses.
  • The frontal lobe does not fully develop until between 25 and 30.
  • The frontal lobe during this time is use-it-or-lose-it—new connections are preserved and quickened, while unused connections waste away through pruning.

Calm Yourself

  • “The art of being wise is knowing what to overlook.” — William James
  • “Twentysomethings and their active amygdalae often want to change their emotions by changing their jobs.
  • “Research shows that people who have some control over their emotions report greater life satisfaction, optimism, purpose, and better relationships with others.

Outside In

  • A fixed mindset is black-and-white thinking.
  • Decades of research in schools demonstrate that a fixed mindset diminishes success.
  • “Confidence doesn’t come from the inside out. It moves from the outside in. People feel less anxious—and more confident—on the inside when they can point to things they have done well on the outside.”
  • “Real confidence comes from mastery experiences, which are actual, lived moments of success, especially when things seem difficult.”
  • Confidence is trust in one’s self-efficacy to produce the desired outcome, and that trust can only come from having gotten the job done many times before.

Getting Along and Getting Ahead

  • After thirty, our thoughts, feelings, and behaviors are highly stable.
  • “Our personalities change more during the twentysomething years than at any time before or after,” which means our twenties are the best time to invest in and change ourselves for the better.
  • Studies show that people become happier across their twenties. We become more emotionally stable, conscientious, socially competent, agreeable, cooperative, confident, and less angry and anxious.
  • “Feeling better doesn’t come from avoiding adulthood, it comes from investing in adulthood.”
  • Working towards things we want makes us happier even if we come up short.

Every Body

  • “The availability heuristic is a mental shortcut whereby we decide how likely something is based on how easy it is to bring an example to mind.”
  • “Compared to our twentysomething selves, women are about half as fertile at thirty, about one-quarter as fertile at thirty-five, and bout one-eighth as fertile at forty.”
  • “Being a parent is nothing to be idealized. As meaningful as it can be, it is also unrelenting hard work.”

Do the Math

  • Unmarked time becomes condensed in our minds.
  • Present bias is discounting future rewards in favor of rewards today, a core problem behavior experienced by everyone.
  • “It’s [present bias] a human tendency, one that underpins addiction, procrastination, health, oil consumption, and yes, saving for retirement. It is often difficult to imagine and give weight to things that will happen down the line.”
  • It takes work to connect the present to the future.
  • “There is a big difference between having a life in your thirties and starting a life in your thirties.”
  • Feeling distant from the future leads to abstract thinking, and abstract thinking leads to more distance.
  • “Twentysomethings who live beyond time usually aren’t happy.”


  • “Almost every twentysomething client I have wonders, ‘Will things work out for me?’”
  • “Deep down, twentysomethings want to be taken seriously, and they want their lives to be taken seriously. They want to know that what they do matters—and it does.”
  • “The future isn’t written in the stars. There are no guarantees. So claim your adulthood. Be intentional. Get to work. Pick your family. Do the math. Make your certainty. Don’t be defined by what you didn’t know or didn’t do. You are deciding your life right now.”

Related Resources

Here is a list of resources, including authors, books, websites, podcasts, and concepts mentioned in The Defining Decade, which might be helpful for further learning.


  • Socrates
  • Sheldon Kopp
  • Erik Erikson
  • Mark Granovetter
  • Rose Coser
  • Christopher Bollas
  • Karen Horney
  • Richard Sennett
  • Anthony Giddens
  • Voltaire
  • Charles de Montesquieu
  • Kay Hymowitz
  • David Brooks
  • Rose Wilder Lane
  • Rom Harré
  • Masud Khan
  • Leo Tolstoy
  • Søren Kierkegaard
  • George A. Dorsey
  • Michel Siffre
  • Laura Carstensen
  • John Irving

Books and Publications

  • The Strengths of Weak Ties by Mark Granovetter