Personally, I simply refuse to work in the office beyond a certain point. I'll print out some code and take it to a local Denny's to smoke, drink a pot of coffee, and scribble on this stupid piece of paper.

I'm also taking Thai Boxing. If you've never gone and beat the snot out of a helpless bag for an hour, I highly suggest you do so. Your day could've sucked for hours and hours, but it's all ok, nonetheless.