in the course of handing out unasked-for relationship advice, i managed to articulate a particular issue in a way i rather liked, so i thought i'd repeat it here for posterity (or at least for my own future reference, since it's an idea that needs to be beaten forcibly into anyone who spends a lot of time hanging around me):
rule #1 is this: you are not responsible for each other's happiness. you're responsible for treating each other with the kindness and respect due the person one sleeps with; however, if that, and the pleasure of your company, isn't enough, there's a problem.
if you let yourself feel responsible for someone's happiness and they have a disorder that makes it difficult, if not impossible, for them to reach the happiness benchmark you consider normal, you might as well just save everyone the angst and go roll in a pile of broken glass, followed by a vinegar bath and a thorough salt scrub, to get the masochism out of your system.