When you were a child, you played tag. You swam with friends until someone made you get out of the pool. You raced your sibling from the outfield to the concession stand, and competed in hopscotch and jump rope.

These days, instead of playing, you exercise. And exercise is, well, boring. You have to take a deep breath and make yourself do it. Gyms know this, so they install a bank of TVs in front of the cardio equipment to give your mind something to do while you’re on the stair stepper. Boredom may even lead you to quit exercise.

So why is exercise so dull and play so fun?

In exercise, there is little mental engagement because there are usually only a handful of choices: you either finish your 30 minute run on the treadmill, you give up at 20, or you stick it out, but walk the last 10. Over and over again. And you don’t really get “good” at exercise; you just get faster or last longer. The lack of mental stimulation makes it not much fun, and easy to skip if something potentially more engaging comes along.

Play, however, engages your mind because there are thousands of unique situations for you to tackle during play. Your ace racquetball opponent might serve you a Drive, a Z, a Jam, or a Lob; you have a choice on how to return the ball and then there will be another new variation when your opponent hits it back. You can get good at play, become an ace yourself, and drive fear into the hearts of your opponents. Because it is ever changing, play is fun, and you become increasingly drawn to it.

And there are so many ways to play. Some involve competition with others, like basketball or laser tag. Others involve competition with yourself to get better, like salsa dancing or rock climbing. Still others are non-competitive, but involve learning movements that allow your mind to flower, such as yoga or tai chi. And if you like running on the treadmill, you’ll love trail running.

Find a pickup game, find a class, find a team. Play to your heart’s content.