You should leave when:

1. You begin remarking to yourself that you drank more than you intended
2. You start consuming substances you swore you wouldn't touch again
3. You need to wipe the salt off a Margarita glass lest you vomit
4. A fellow partygoer claims to have a lot of respect for you
5. The room starts spinning
6. The hostess asks if you're ok
7. Maybe it wasn't the hostess
8. You stand up and immediately fall against a brick wall

I ignored the first seven.