Think of a memory you want to stop thinking about.
Notice the sub-modalities. Freeze-frame it and shrink it in size.
Skip to the end of the memory and freeze-frame it, and imagine a whiteness knob and grab it, whiting it out really quickly.
Repeat this three times.
See yourself in the end of the movie and run the movie backward, seeing the sights backward and the sounds backward and spin the feelings in your body in the opposite direction.
When you try to think of the bad memories, the more you do this, the harder it is for you to remember them.