Likewise, at 21 or 25 or even 29, one good conversation, one good break, one good TED Talk, can have an enormous effect across years and even generations to come.
It's as simple as what I learned to say to Alex. It's what I now have the privilege of saying to twentysomethings like Emma every single day: Thirty is not the new 20, so claim your adulthood, get some identity capital, use your weak ties, pick your family. Don't be defined by what you didn't know or didn't do. You're deciding your life right now.