Keeping score is a behavior that will quickly unravel a relationship. It begins innocently enough, but it ends with huge fights, lots of resentment and plenty of hostility.
People who keep score often begin this behavior as a way to teach the other partner a lesson. Hurt within the relationship is never just hurt; it turns into wanting to hurt someone else so he/she will suffer and know what it feels like. The problem with that is that we are all sensitive to different things, and what hurts one person looks childish or punitive to another.