Thought stopping technique is so ridiculously simple, that it is impossible to understand its power until you implement it on a regular basis.
This is the gist: if you find your mind wandering down any rabbit holes that have the potential to throw off your equanimity, stop the thoughts in their tracks.
How, you ask?
TELL THE THOUGHTS TO STOP
In your head or aloud, say the words STOP. Picture an EXIT sign. Imagine a dam redirecting water.
Do whatever it takes to stop shitty thoughts in their tracks. Do it enough and it will become a habit.
Need an assist? Wear a rubber band around your wrist and give it a nice SNAP if you find yourself thinking about unhealthy things.