Rumination

I found it hard to figure out I had ocd too because my main compulsion was Ruminating too. As for the "just don't ruminate" advice, if that's without paraphrasing I feel as if they don't understand the condition at all. So it's going to take a while to get better at it but you almost have to wait until you're Ruminating and catch yourself at the start. Accept that they are thoughts then refocus your attention on something else, some positive or grounding techniques. You may start to get stressed by it but that'll probably be your proof it's a compulsion and not a "normal" thought. Do you know what to do when you notice your are Ruminating other than that?

The first part is to learn to observe your own thoughts so you can acknowledge "I am ruminating" Mindfulness practice is what helped me the most. It takes time to learn but with time you find out that you can direct your attention and you can stop ruminating. Greenberg is no fan of mindfulness, and I don't get why, I think it's very important to learn if you don't wanna a be a slave of your thoughts and emotions.

Rumination is one of my main cumpulsions too. I think one way that kinda helps is to direct your attention to something productive that stimulates your brain and body. Then eventually we can get to a point where we use mindfulness easier.