How do you just stop caring?

I just want to put it out there that I have zero feelings for Harriet's father. I'm not fully indifferent though, I'm still struggling with all the situations he put me in and the emotional distress he caused me. How do you get past that? Every time he tells me, oh-so-sensitively, about another conquest, another engagement (I kid you not), I just feel so much hate. And the most annoying part is that he attributes it to jealousy. I feel all this emotion towards him because I cannot escape him. He will always be in my life, and he doesn't deserve it. This is not me commenting on him as a father by the way, as a person in general. Imagine the worst relationship you've known, horrific break up and a very insensitive ex. And then someone tells you that you need to talk to them everyday. Some days it makes me want to change my number and move away to never hear from him again. I never would as I will push Harrie and him to have a relationship for as long as she wants it, for ten years or forever. But I just wish I didn't have to be involved.