I'm on a similar wavelength as Cheshire. A lot of self correction, and just plain old distraction. My current job leaves me essentially 8 hrs to just think, which much of the time for me is a terrible thing. If I start to have a bad thought, and thank whatever higher power you're into I can listen to my ipod, I put on upbeat music I know all the words too. Usually singing, or usually just mouthing the words is enough of a distraction to at least keep me from obsessing.