Dreams.

I remember it clearly; I sometimes have dreams where I'm running on all fours, and very quickly. Sometimes, even in the process, I lower myself onto all fours, as if it's a faster way to run. And I know where this feeling comes from. When I was in preschool, I was at some kind of sports center, and there was a kind of arena with pieces of foam scattered inside. I moved around on all fours because it was uncomfortable to walk on two legs; I kept tripping and falling.