Selfish in My Bad Thoughts

So it seems everyone else in this world is allowed to be selfish, the moment I am, I’m the bad person. This is what happens when you keep doing things people didn’t ask you to, when you keep sacrificing for them, again, without them asking you to. When you keep caring more not hurting them, but think it’s alright for them to hurt you. They just get used to your niceness, that they don’t even consider being grateful, you are taken for granted and always expected to put them before you put yourself. But then? They have always been selfish, they have always treated you the way they have, so how does it matter?