In the years just after I finished college, when I was working full time and living in DC, I was very concerned with the question, "Am I an adult now?" I very badly wanted to answer in the affirmative and worked hard to make it so, but when so many other people your age are still behaving like children, it's difficult to distinguish yourself as invisibly more mature. So I was always wondering when I would reach a point where my adulthood would be incontrovertible. Then I went to grad school, where the adulthood project had to be aborted as a matter of necessity.
But now, it is a lot easier to see the marks of adulthood. For example, I am drinking a cup of decaffeinated coffee. Ever since I started drinking coffee in college, I used to wonder at decaf coffee drinkers - for why? Coffee doesn't actually taste good; it's essentially a low-grade productivity drug to help you read more books and write more words, faster. Drinking decaf coffee is like taking placebo aspirin for a headache.
But now I see things differently. It's like the hat/elephant drawing in The Little Prince. Children are defined as those who see the elephant in the gullet of a boa, adults as those who see a hat. Neither can satisfactorily explain their perspective to the other.