Another example, this only started in the past few years, is that every time I pick up (or even see) a metal fork I instantly intensely imagine smashing and grinding my teeth out with it. Almost every meal I eat with a fork is unpleasant because I'm trying to force that image out of my mind. I have a real issue with teeth to begin with.
As for the knife / urethra thing, I literally nearly passed out at work earlier because my mind wouldn't stop visualising it. You don't get how bad these mental conditions can get on a moment-by-moment basis.