There's two really good approaches to this issue that I've learned. The one in the article is cognitive behavioral therapy (also, dialectical behavioral therapy, depending on the type of ruminations). Another approach that has been gaining more traction lately is mindfulness, which is basically using meditation to clear the mind of ruminating thoughts. I've read bits of Feeling Good Handbook, which is an often recomm…
I've noticed a stead improvement after using it for a while.