Feeling low because of past experiences. [I Battle Depression]

The people I have come across with only care about themselves and as soon as your relationship with them terminates, they treat you like dirt because you mean nothing to them anymore. They treat you like dirt by degrading you, comparing you and doing the best they could to hurt you just like anyone else. They make you question why you even bothered with them in the first place. I learned that these kinds of relationships show that people want you when you are convenient, and when you are no longer of use to them (lost interest, no longer care), they become hostile. In their eyes, they have already disposed you, so they treat you like trash, just like others who have hurt you before. Why should they be nice when they have ended a relationship? Because in their eyes, you no longer offer the things anymore, so they show their true colours and simply not care anymore. This makes you realise the only person you thought cared about you, no longer cares anymore, because they start degrading you and turn into the word person you could imagine. Others, are just the same - they hurt you too.