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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.



Mind and Body


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.