1. You make up a lame excuse about your drunk friend and leave ASAP
2. You start to have sex, change your mind, and leave. Usually results in you earning a reputation as a blue baller
3. You have sex with them because you don't want to piss anybody off and feel like shit about yourself the morning after
You usually have about five seconds to make up an excuse to get out of the situation before it becomes socially awkward to do so later.
Even if you break out of the loop in the first few seconds, you will usually be asked to leave the party.
"I almost got stuck in the room loop last night, but I got out of it by pretending my friend had texted me and needed me to buy her a pregnancy test"