I learned that nothing sends a person into a tailspin quicker than feeling he is not valued or respected. I believe people have an interior dialogue going on in their head, causing them to react the same way each time they are hurt. When we stand in front of an elevator and push the button, we know the elevator will arrive and the door opens so we can get in.
People have buttons just like an elevator. You can push a person's buttons by hurting them and you can be sure that something will come out of that person. It may be withdrawal, depression, anger or they try harder to please you but in most cases they will hurt you back.