I’ve long been haunted by the idea that I am immature. That I haven’t grown up, or that I’ve failed to grow up at the same rate as everyone else. That despite stellar academic performance, I’m behind on life.

What does it mean to be a grown-up? Once I thought it had to do with the literal age of your body—as you grew up you passed milestones and accrued privileges, like watching PG-13 movies and driving and voting. At the end of this process, or at some important point (around high school graduation), you came of age and were accorded all the rights and privileges that any adult should enjoy. You became a grown-up.

But some children in hardscrabble environments are said to become grown-ups very quickly and some adults in pampered milieux are said to never grow up. So maybe it seemed to have something to do with accumulating responsibilities. You became a grown-up not when you passed a milestone of age, but when you handled enough responsibility that you could take care of yourself independently. Or maybe when you could support others. I never figured out what the threshold here was.

But I have accumulated a lot of responsibilities. I work at a job and I pay my own rent and utilities and I clean my apartment and I cook my own food and I pay my own taxes. I can take care of myself independently. I can adult. Yet I still don’t feel like a grown-up. I still feel like a ten-year-old soul frantically manipulating the strings of a twenty-five-year-old marionette. I still feel like there’s some distant nebulous place out there called the Real World that I have not yet been thrust into. Like I’m treading in the shallow end of the pool.

Do you become a grown-up the day you stop thinking of it as “adulting”? You can only become a true grown-up when you stop worrying about whether you’re a true grown-up? There’s something sort of Zen about it.

Or maybe it’s street smarts. Maybe when you’re not naïve anymore, you’re a grown-up. I once got swindled out of $200 by a stranger with a sob story about her aunt in a hospital, which I’m pretty sure was fictitious, and I felt like my naïveté was fully exposed that day. I am unwise to the ways of the world. My kneecaps have not yet been broken in by a baseball bat swung by Society. Maybe you’re a grown-up once you can conduct yourself in a way that tells pickpockets that you’re not an easy mark. Once you can stand your ground against car salespeople trying to upsell you. Once you can read people and tell a good manager from a bad one. Once you’re not a pushover anymore.

Maybe all of these are just aspects of grown-up-ness. Each of them marked by a different set of developmental milestones. Maybe grown-up-ness is just one of those you-know-it-when-you-see-it things, like pornography.

Lately I’ve been thinking a lot about developmental milestones. It’s the halfway point of the year, and at the beginning of the year I set myself several goals. They’re things I want to try, or skills I want to master. Some of them I’ve passed spectacularly, like Learn to bake or Write 50 words a day that nobody else will read. Some of them I have barely started, like Learn to sew or Learn Cantonese/Tagalog. But really they’re there as a motivational tool, to encourage me to hit long-overdue developmental milestones.

I’ll hit another one to-morrow. In seven hours I will drive to San Francisco and check off Become comfortable with long drives and highways.