I found that for me it is very difficult to just stop doing something. But I found it works when I instead of stopping go for replacing it with something else. The difference is subtle, but still there is a differnce.
So, for example if I feel I start obsessing about about something, I take a book on some difficult subject that interests me and I start studing. When my mind starts drifting back to the problem, without beating myself about it, I remind myself that is something I can not control, and that worring and obsessing will only drive me crazy, and than I chose not to drive myself crazy.
I believe we can control our minds, as long as we are patient and gentle with ourselves.
I guess this sounds crazy
, but it works for me.