Some of the acceptable reasons:
1) I am stuck in surgery and will not be done for another 10 hours.
2) My relief worker has not shown up yet.
3) I have to work that day and the next day too.
4) I am currently in a different state/country.
1) I am tired and want to stay home.
2) I really do not want to deal with crowds.
3) I am straight up lazy.
4) Who's birthday is it?
5) Why am I celebrating? It has nothing to do with me.
WWJD? Clip them and never look back. Pull a passive aggressive maneuver and use some other lame ass excuse. Brag about how awesome the party was and nothing will compare. Be thankful for the day, period.