Same here. I go out for a bike ride or chop down a tree etc for a couple of hours every afternoon. I also find good ideas or solutions to difficult problems turn up faster when I'm away from the computer for a while. It's highly recommended not to spend 18 hours a day on the PC, although I do my fair share of that as well.
Physical exercise, going outdoors & socializing in general. Most of my work is a very indoors & isolated process, and I need equal amounts of "outside" activity to keep the cycle in balance and feel refreshed.