If you're an asshole just don't text me! in All of Me

I mean,why?Just why?Every time my ex texts me,he puts me in such a depressed mood.It sets me back.I want to block him but I don't know how.

I should probably let go of all my feelings for him,but it's hard.Im over him and I don't want to be with him,but I still get sad and angry when I think about him or his son.I don't really think about him much until he texts.Which he did.Annoying.