I totally blew off my 20th a few years ago. Of course I had lived back in that town for almost a decade... and the only friends of mine from HS that I care to spend time with I already spent tons of time with. So... I didn't need to go there to remind me what a bunch of losers I went to school with.
I can't remember the comedian who said it, but "If I want to see people I went to high school with, I'll order a pizza."