Get a hot naked girl to give you a massage, works wonders for me. :thumbsup:
Seriously though, Matt_vp has some good suggestions, really its amazing how much it can help having a chat to someone. Another thing is to take some time out to do something you enjoy. Go out for a drive just for the hell of it, just head out onto the highway, put some nice music on, and just enjoy the drive. Go to gym, if you enjoy that. (seriously, I find going to gym is one of the best ways to relieve stress) Play your favourite computer game, watch your favourite movie, or hang out with your friends...just do something you enjoy that takes your mind off whatever it is thats bothering you.