What I've been doing since mine:
Day of: cry like a baby cuz it sucked
Day after: got that new tattoo I wanted since I wouldn't be spending any money on him (take out to dinner, etc)
Ever since: work my normal hours, then straight to the gym. Signed up for a few extra sessions with my trainer, a few new group classes and during my lunch hour I do yoga.
I also started applying for graduate studies programs and had my friends introduce me to some new people to hang out with. Make the best of a shitty situation...it is all we can do.
I did, however, take one day (we broke up on a Monday, so I pushed it to Saturday) to mourn the loss, cry it out, eat some skinny cow ice cream and just get the negative shit out. Gotta do what ya gotta do.