if you are worried about making a decision you will regret then instead of breaking it off right away maybe try this-

give yourself a timeline. say in 4 months if things don't improve, call it quits. That way you can still try whatever it is you need to try but not end up being one of those people stuck in a dead relationship. the key is that you HAVE to break it off after the time limit is met. It's what keeps you from screwing yourself over. This way you can get out of the relationship knowing you did what you could and not have regrets while protecting yourself.