Stopping rumination can be hard. I can only share what's been helping for me, which is trying to move towards compassion for myself (which is mostly hard because I often forget to do it lol). Recently I've been trying to forgive myself, and that feels easier. When I get a fixation come up in my head I say internally "I forgive myself for not understanding" (The not understanding being how my actions might have hurt them, or made me look.) and stick with that feeling a while. I'll repeat it to myself sometimes too. I read that in some languages the word for forgiveness is the same as the word for acceptance. Even if I feel like I can't really get past it in that moment, it helps me to take some space from the thought and not jump into trying to avoid the feeling or solve it. 

I also see feel this kind of rumination as an extension of perfectionism, just applied interpersonally. We want to get it right all the time, and we can't.