Tbh I've felt more shit through sex in some of my relationships than through casual sex ...
I guess I always went into a one night stand or casual arrangement, not expecting to get much from it, and you don't have to go back. But in a relationship you are kind of stuck with it. I think it becomes more if a let down because by the time you sleep together you are more invested.
I'm probably weird in my thoughts though. I mean I kinda viewed it as a chance to work out what I liked and didn't like before I got into a relationship, and even work out what the men liked so I had a few tricks up my sleeve...
Mind you my self confidence and self worth was shot way before I was even old enough to have sex.