How do l stop caring for him and always focus on school and myself?

So obviously l like this guy and stuff. But l really want my main focus to be at school, myself, my well being and self love for myself. I don't want any relationship with this guy so how do l get rid of these feelings, l mean like l want to have these feelings for school and myself not for him, l also want this cause this guy makes me feel like shit, l thought he was my best friend but all he cares about is himself, and once he does that to me he feels good about it, l don't want to feel that way ever again so please help anyone.
How do l stop caring for him and always focus on school and myself?
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