I hate ruminating as well. For me its usually about a negative future I predict for myself. Needing to give up my pups and then becoming homeless. Or worse, dying before I'm able to see my pups on their final days. I don't do very well in breaking out of it, mostly just riding it out. I can sometimes catch myself doing it and focus on something else. Walking my pups or at least giving them a good snuggle. Trying to be in the here and now, rather than this terrible future that probably won't come to pass.

I hope this helped. Be well.