Carl,
I myself learned the same lesson on New Years. Despite all our denials and bravado about becoming experienced citizens, the inescapable facts are these: 1. Hangovers hurt a bunch more than they used to. 2. We're simply not as bulletproof as we once were.
Sounds like you had a great birthday though. I think you should call in sick today. Have a pot of coffee and some greasy bacon and eggs and go back to bed.