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# Summarization of:The Defining Decade: Why Your Twenties Matter and How to Make the Most of Them Now

### Meg Jay

I saw a post on r/books about which self-help books are actually useful, and one of the top comments recommended The Defining Decade. I had never heard of the book, but the premise - that your 20s are critical years in setting up the rest of your life and that these years are too frequently not given sufficient forethought - resonated with me.

The opening paragraph cites a 1991 study in which the lives of 49 eminent psychologists are examined for the events that had the strongest influence on how a person's life unfolded. While these autobiographically consequential events were sprinkled throughout the lives of the psychologists, the highest concentration of events was centered in their 20s. By age 35, roughly 80% of these significant events will have passed. In many ways, this makes sense. Our 20s are when we transition from living under parents to establishing our careers, our spouses (and perhaps our children), our living conditions and more. And although there's nothing that chains us to these years, it's certainly harder to pivot to a new direction once a house has been bought, a formal agreement signed with a spouse, and specific professional skills acquired.

The book makes a claim that there's an ongoing cultural shift that minimizes the importance of wasting one's twenties, but I find the claim to be poorly substantiated and irrelevant; after all, I don't decide how I spend my time based on what strangers I've never met are doing.

I've extracted from her advice the elements that seem most important to me. As she does, I aggregate based on subject matter.

### Work

• Young people can struggle to find meaningful, important roles. The choice then becomes unemployement (because nothing is interesting) or disappointing employment (e.g. working at a coffee shop). However, both are nearly equally likely to negatively effect people (e.g. cause depression). By contrast, underemployment can be advantageous if it builds identity capital i.e. collection of personal assets including our experiences, where we're from, how we speak, etc.
• 2/3 of a lifetime wage growth occurs in the first 10 years of a career. Salaries peak and plateau in the 40s. If money matters, the best time to climb is in your 20s and 30s.
• Strength of weak ties: some study shows that 3/4th of new jobs come from contacts seen only rarely or occasionally. The reason why is that the people we see most frequently (our closest friends and family) are closest to us in terms of resources, connections, interests. Stretching outside of one's circle of friends can be uncomfortable, but it's a fantastic way to help one's career.
• Ben Franklin effect: people who you ask for help will like you better. Asking for something extremely general is not usually help. A better approach is to identify the person's expertise, present yourself as a serious person with a need matching the person's expertise and then ask a specific question
• Pride is expensive
• A person's identity comes from maintainig a particular personal narrative. This isn't just important professionally - it helps a person's emotional state. That narrative is more psychologically stabilizing if the narrative is affirmative/constructive

### Family

• Living together with a significant other prior to marriage increases dissatisfaction and probability of divorce. Being engaged while living together does not have the same effect. Couples who discuss intentions and goals before acting typically do better.
• Vacations to 3rd world is great preparation for marriage. It's enjoyable, but frequently filled with painful, unavoidable problems. You can see how someone reacts and they can see how you react. High neuroticism (e.g. flipping out at really small problems) is usually lethal for a relationship.
• Beyond interests and physical attractiveness, it can be helpful to understand how your significiant other operates. Jay suggests considering five dimensions (openness, conscientiousness, extraversion, agreeableness, neuroticism). Usually having matching traits means relationship will go better.

### Mind and Body

• In 20s, our brain starts learning how to better regulate ourselves. Research shows 20 year olds react more poorly to negative feedback than older people.
• Controlling emotions is essential. People with better emotional control report greater life satisfaction, optimism, purpose, relationship satisfactions, etc.
• Growth mindset. Those who see criticism as a punishment will struggle to grow. Those who view criticism as a feedback mechanism for improving will grow much better.
• For the most part, personality seems to be fixed after age 30
• Getting along and getting ahead makes us feel better. Goal setting in 20s leads to increased purpose, mastery, agency.

### Fertility

• Awkward to discuss, but critical! Women's fertility declines sharply after 30. Harder to conceive, complications with pregnancy and baby more likely.
• Best time to have children coincides with peak earning years. Couples need to discuss tradeoffs and choose, or consider alternatives like babysitting or grandparents

In general, research shows that the brain overemphasizes the present. Having abstract life goals makes them distant, and your brain correspondingly weighs them less. You can counter this bias by working backwards to turn long-term goals into concrete present actions.