I have a similiar issue of being drawn to someone I know is absolutely no good for me.... I totally get the whole belief that if you give up on a friendship you somehow prove it meant nothing, which means the whole thing was one very very big waste of time...... Which is t true but I also can't...
I'm going through something similiar.... It's hard when you have no one else to turn to..... I'm hoping to find the strength to leave those people behind that don't really care about me, hope you can too.