Even a slight shift in your 20s can radically change where you end up in your 30s

Dr. Meg Jay explains why your 20s matter

Joanne McHugh

Sep 02, 2025

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Your 20s matter. 80% of life’s most defining moments take place by age 35. Two-thirds of lifetime wage growth happens in the first 10 years of a career. More than half of us are married, or dating, or living with our future partner, by age 30. Personality changes more during our 20s than at any time before or after.

According to clinical psychologist Meg Jay, researchers at Boston University and University of Michigan examined dozens of life stories, written by prominent, successful people toward the end of their lives. The researchers found that ‘autobiographically consequential experiences’--the circumstances and people that had the strongest influence on how lives unfolded–were most heavily concentrated during the 20-something years.

Jay covers the separate–but interwoven–critical periods that unfold across the twentysomething years and shares what psychologists, sociologists, neurologists, economists, HR execs, and reproductive specialists know about the unique power of the 20-something years She also challenges some media-driven misconceptions about your 20s and shows how common wisdom about the 20-something years is often wrong.

“The twenties are the years when it will be easiest to start the lives we want. And no matter what we do, the twenties are…a time when the experiences we have disproportionately influence the adult lives we will lead,” said Dr. Meg Jay.

“With about 80 percent of life’s most significant events taking place by age thirty-five, as 30-somethings and beyond, we largely either continue with, or correct for, the moves we made during our 20-something years,” said Dr. Meg Jay.

“In the twenty-something years, even a small shift can radically change where we end up in our thirties and beyond. The twenties are an up-in-the-air and turbulent time, but if we can figure out how to navigate, even a little bit at a time, we can get further, faster, than at any other stage in life,” said Dr. Meg Jay.

“The post-20-something brain is still plastic, of course, but the opportunity is that never again in our lifetime will the brain offer up countless new connections and see what we make of them. Never again will we be so quick to learn new things. Never again will it be so easy to become the people we hope to be,” said Dr. Meg Jay.

“Twentysomethings who use their brains by engaging with good jobs and real relationships are learning the language of adulthood just when their brains are primed to learn it...They learn to get along and get ahead, and this makes them happier and more confident. They learn to be forward-thinking before life’s defining moments are in the rearview mirror,” said Dr. Meg Jay.

The Things Your Mom Should Have Told You Book of the Month is The Defining Decade: Why Your Twenties Matter–and How to Make the Most of Them Now by Dr. Meg Jay

In the olden days, moms used to clip articles from newspapers for their kids if they thought it was something they needed to know. I’m keeping an eye out for things that you might have missed that may be helpful to you.

This week’s clips:

Why do you feel so drained after spending time with certain people? The Calm Journal runs down a list of toxic personality types and offers tips for protecting your peace.

On an episode of Michelle Obama and Craig Robinson’s IMO (In My Opinion) podcast, dating coach Logan Ury shares her go-to strategies for a first date, why you shouldn’t care so much about whether there’s a “spark,” and how to find an authentic connection in a dating world mediated by technology and phones.

You’re kayaking in the Everglades and an alligator surfaces near you. How should you respond? Take a New York Times quiz (gift link) to test how much you know about staying safe around animals like alligators, bears, and stingrays.

It was an honor to be featured in Abbey Algiers’ latest edition of “Who I’d Rather Be Talking About.”

Among other things, Abbey wanted to know:

What my daughters think about me giving life advice to 20-somethings
If I could only give one piece of wisdom to readers in their 20s, what would it be?
Which topics I’m eager to cover in Things Your Mom Should Have Told You
The best advice my mom ever gave me

If you want to know what inspired me to create TYMSHTY or discover my unexpected talent, be sure to have a look.

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Things Your Mom Should Have Told You

Even a slight shift in your 20s can radically change where you end up in your 30s

Dr. Meg Jay explains why your 20s matter

This week’s clips:

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