I guess I try to remain sensible about it because I have seen how I and others make wrong decisions with who they sleep with. Even with my boyfriend of 3 years is told no quite often because I still don't kinda trust my judgement of when to have it ever since his mum barged in and totally went bonkers. Now I will tell him no when feel like it to kinda enforce my power over the situation because I feel that because he is spontaneous/impulsive with me he wont think about the possible consequences - like utter embarassment + shouting from the mum.
Tbh though, I think I've accepted that I am mature enough to choose correctly who to sleep with (if I was single) but now can get easily turned off knowing that the bed is adjacent to the wall that my boyfriend and his parents share :\ and this bed is SQUEAKY.