We forget to play. It's very easy to get caught up in being an adult and all the responsibilities that go with it. When we forget to play, we stop learning, we stop experimenting, and we stop exploring.
Whatever your favorite pastime, give yourself permission to not be perfect at it. For example, if you are skateboarding, go ahead and fall trying a new stunt. If you are hiking, take a new path that you haven't hiked. If you are painting or drawing, let yourself get sloppy, just freeform it for a couple sheets. If you are a musician, play incongruent notes or try a new technique.
Regardless of your pastime, the point is to push yourself in a direction you haven't gone. Don't worry about the end product or result. You aren't trying to be perfect and you aren't trying to please anyone. Just have fun trying something different.