When my ruminating gets triggered it's after I experience a disappointing outcome to a situation. The pandemic has really triggered my bad habit of rumination/dwelling because I'm socially isolated with zero support.

Once you figure out what triggers your habit of dwelling on the past, you can learn to stop dwelling. But that takes a lot of practice. One thing that I learned from my dwelling, is that it is my way of trying to change the past. But as we all know, you can't change your past. You are stuck with your past. All you can do is try to move forward which is super difficult to do.