guy this is for you... what would you hate your girlfreind to do the most??? to you?
Yeah, being cheated on is the worst, but since you said bad habit. I'd hate for my girlfriend to constantly bring herself down. Like if your girlfriend always comes up to you like "oh man this dress makes me look fat!" But she really doesn't, so those are tough problems to deal with.
I cant think of anything worse than being cheated on.