There are techniques to stop repeating thoughts over & over again. Here are some that I use (in no particular order):

1. I imagine a huge stop sign with a beautiful landscape behind it or just the stop sign by itself and focus on it. Make it an extremely detailed and realistic picture.

2. Get back into the moment. Focus on something else or try to rationalize the thoughts that you are experiencing. Sometimes I obsess over me being a monster somehow so I say to myself "A monster would do things and NOT regret it. I haven't even done anything and have no desire to, so how would that make me a monster?"

3. Here are some other techniques:

http://cognitive-behavior-therapy.co...ry-rumination/

Obsessive thinking is no game & can feel miserable. Hoping that you find some relief from this soon!