I haven't ever dumped anyone. It's usually me being dumped.
But if I were to dump anyone, it would be awfully hard I imagine. I'd hate the idea of it, but I guess if I had a validating reason...but knowing it may hurt the other person is a major factor. That's why I've never really been the one to do it.
But I'd never cheat, even if things were going bad. And I don't think there are any justifiable variables that make it right. Plus..if I'm in a relationship with someone, then they aren't going to be a person that I would ever in a million years think about cheating on. Relationships are hardcore. No funny business, it's not worth it and just shows you like to play games.