This may sound dumb, but it's kinda the equivalent of the stereotypical chick breakup therapy of eating an entire container of ice cream while watching a romantic comedy. So here goes: Since you're picking up food anyway, pick up whatever is your comfort food, stop by your nearest movie rental place (or if you can stream movies on Netflix or something, that's cool, too), and just pick up something mindless and fun, preferably with a lot of action, and just veg out.
My other option is to drum, loudly, and for a long time. But if you don't play drums, that won't really work for you.
Sorry about the rough day, dude.