When someone is leaving you, it seems that the situation is as bad as it gets, so you might decide to tell them everything you think. When we are angry, we often say rude and offensive things, we throw away their stuff and try to make it look like we wanted to break up too. It seems that this behaviour is saving your ego, but it will only make things worse.
Why it’s harmful: The anger will disappear pretty quickly and, if you said a lot of things you shouldn’t have, you will feel ashamed. You might even think that the person left because you were rude. And even though it’s not true, you could keep blaming yourself for a long time, or even worse — keep trying to fix it. By doing this, you might do even more ridiculous things, humiliating yourself.