Why do we go back?

I think we generally keep talking to our ex that hurt us because you may feel that maybe it was just one incident and it won't happen again. It's human nature to make mistakes right? And also maybe we still look at all the good times that we had with that person and feel that it could be that again. But once a person hurts you (i.e. physically, mentally, or cheated) that will alway linger over the relationship and could possible happen again with that person. Sometimes you should let go of past relationships and move on. I think we look around for compassion and care from others because deep down inside we know that we are not making the right choice by talking to our ex that hurt us and we need a slap in the face so to say from a friend to wake us up.