I was in St Albans, England, walking through the sunny park leading up to the cathedral, when I saw a small boy rolling down the hill in the grass. I felt something unexpected: jealousy. I wish that were me. Followed immediately by a second thought: Why couldn’t it be?

I could, in theory, roll down that hill. But at what expense? Dirtying my clothes? Looking like a lunatic? In about three seconds, the case was closed. I kept walking.

What unsettled me wasn’t that I didn’t do it but rather how fast I didn’t, how automatic the verdict was. I was no longer someone for whom rolling down a hill was even an option.

Somewhere along the way, I, like many adults, became so aware of how others might perceive me that I stopped allowing myself to play freely. The problem is that play isn’t frivolous — and by denying playful impulses, I could be holding myself back.

Play is not just for kids

Neuroscientist Jaak Panksepp found that the desire to play isn’t a behavior we learn or a phase we’re destined to grow out of.…