Don't sign up for a relationship that you're going to replace out of because you "aren't interested".
Don't rage quit relationships. If there's someone in the relationship you hate and are going to rage quit because of them, don't sign for the relationship they are in. For the relationship you're already in, grow a pair and finish.
If you're replacing out of multiple relationships because of anger/restraining order, or disinterest in relating, take a break. Don't put the innocent in a situation to have to replace you just because you're being a little bitch about things.
Just don't do it.