Feel like I've mentioned this recently in another thread, but if I don't do some static stretching at least a couple times a week when I'm training heavy, my back progressively tightens up to the point I can barely walk. GqArtguy said something about some eccentric BW squats postworkout to help with knee pain, which I'll probably wind up trying out. Besides that, so long as my warmups are in check I generally feel pretty good.
I'm relatively young though. Still in my 20s.