Fifty years is as arbitrary as any other measurement in time. Yet we regard this birthday as a milestone. Fifty used to mean you were old. Now it’s middle-aged, even young. People like to document 50th birthdays with gag gifts. At mine, I got a cane and an ear trumpet. Funny, huh?

What does it mean to turn 50? It means young people of the opposite sex call you “sir” or “ma’am.” It means cops don’t give you a warning; you get the ticket. Often it marks a period of role reversal. Mom and Dad helped you out when you were getting started. Now, you’re helping them. Chances are, you’ll be doing this while partially supporting your own grown kids. In short, being 50 means, in the eyes of society, you’re a grownup.

Which is a mistake. Human maturity isn’t predictable like the ripening of a piece of fruit. Growing up is a project one embarks on (or fails to embark on), the success of which can be observed at practically any age. A thoughtful person of 25 may be considered wise beyond his years. An 85-year-old may be narcissistic and immature.

So, how do you know if you’re a grownup? One measure is how much you’ve learned. Check out “50 Things You Need to Know by 50," our cheat sheet on sex, food, death, money, and more. But wisdom is more than accumulated knowledge. For a few days I’ve been peppering some of the smartest people I know with this question. Here’s what they said. You’re a grownup when…

• You know there are many things much more important than yourself.
• You’re willing to say “I was wrong.”
• You’re attentive to the footprint you will have left on the world.
• You forgive the carelessness of the young, regret the thoughtlessness of your own youth.
• You finally realize you have no one to complain to.

Growing up is a choice. The journey begins with the simplest of steps: identifying your values, then acting accordingly. This means jettisoning the excuses that have previously blocked your path (“I’m too tired,” “I don’t have the time,” etc.). And then the tricky part: doing all this while retaining your sense of humor. Few accomplish these goals. (Total success would mean being something on the order of a saint.) But the important thing is to point yourself in the right direction and start marching. The alternative is to have a life that has a beginning, a middle, and then just ends.

Steven Slon
Editor, AARP The Magazine
editor@aarp.org

601 E Street NW
Washington, DC 20049