If you could change just one thing about yourself, what would it be?

Personally, I'd like to be able to learn things more quickly and easily, have more energy, and get back the body that I had fifteen years ago. Oops, that's three things. Oh well. I suppose that if I had the body back that I had fifteen years ago, that would probably take care of the other things because my brain would be working as well as it was then too.