Hangovers, headaches, and the like are typically signs of dehydration. That you don't have them is mostly indicative of your tendency to stay hydrated.
I guess what I'm most proud of with my body is the mind that came with it. I learn quick, lead well, speak well, and most importantly respect that others are equally as proud of themselves for similar reasons. Lots of people like 'mindless entertainment', personally, I can't stand it. If my mind isn't constantly stimulated and forced to think, learn, or solve-problems, I'm bored.