IF YOU’RE in your 20s and you think you’ve got, like, a decade before you have to get serious about your future, you’d better think again. Meg Jay, a clinical psychologist at the University of Virginia, is reaching out to that drifting generation of young Americans who imagine they can take a sort of decade-long gap year. In her book The Defining Decade and in a recent TED Talk, Jay argues that 30 is definitely not the new 20. All sorts of clocks are ticking, and 20-somethings may wake up to discover they are 30-nothings if they haven’t built up decent foundations in work and relationships. Jay warns that people who “huddle together with like-minded peers limit who they know, what they know, how they think, how they speak, and where they work.” You’ve got to be open to strangers and strangeness, and paradoxically the online world can make that less likely, not more—something that’s the subject of another TED Talk by Maria Bezaitis of Intel. Jay says being in your 20s is like taking off in an airplane for a long-haul flight: just a little course correction in the beginning can make the difference between heading for Alaska or landing in Tahiti.