Humans are social animals. When it comes to affairs of the heart, most of us are pretty similar. We want to be loved, respected, and cared for. We want to get along with others and generally have a good time with them. When we fight with, reject, or distance ourselves from the people we love, we don't feel good. And when they fight with, reject, or distance themselves from us, we feel even worse. So when you fight with your partner, you both get hurt.