If you are angry or resentful at someone or something, you are giving them free rent in your brain. They are not thinking about you. They are not giving you free rent. Obsessing over how you are going to get even - worrying about what they think about you - wondering how they could act in a certain way: these are just a few examples of how we give others free rent in our brain. Usually this kind of "stinking thinking" leads us to a drink or drug unless we pick up a recovery tool and change our thinking.
If I find I am obsessing over someone else, I will consciously tell myself to just stop it. If I hate someone, I will forgive them in my heart. If I resent someone, I will pray that they get as good a life as I have. I will think of something to be grateful for in this moment. Then I will make a decision to turn my life and will over to the care of my Higher Power and follow what my Higher Power wants me to do in this moment.