When you find yourself swirling down the toilet of negativity, catastrophizing the possible, future, maybe, might, what if, not-yet-taken-place event that is lodged in your prefrontal cortex, try this.
Forcefully say to your ruminating self STOP!
Then immediately and physically turn your body in space and go do something else for a couple of minutes. Tie your shoe, wash your hands, go to the bathroom, unload the dishwasher, get out your exercise clothes, decide what to make for dinner, make a grocery list–you get the idea. Change what your are focused on by shifting your attention both physically and mentally to another task.
After you do this for just a little while, you may be able to return to whatever task or work you were doing before if necessary, newly refocused.
The benefit of briefly shifting your attention is that it gives your body and mind time to get a little distance and perspective on the issue that is bothering you. This tactic will buy you time to pull back from the negativity and refocus. A thought is just a thought, and you do not have to sit with it. It is a choice you can make.