You can also consider the idea of his robbing you. Is it not enough that during the time you spent together, he robbed you of what could have been a better life for you? Should you not cut the losses and stop ruminating, because your rumination means that even without being physically present in your life, he continues robbing you of good time, of what could be a more enjoyable life?

That said, this is just a cognitive idea. I think some rumination is necessary in order for the brain to process and you should let it run its course, because that is how you ultimately will be able to shake it.