Tom, for me, i believe these thoughts just appear in my brain, as you say, because they are ingrained for decades. it is automatic. it is a habit, albeit a filthy one, but a recurrent, constant habit. the first step to stop this addiction is to stop it here. to be aware of the thought and take positive action on it. have a plan before hand. a precise action. ex. when i have one of these thoughts i will pick up a book, go for a walk, exercise, cold shower. etc. anyway, that helps me. the problem is i don't always do it. there in lies the rub, how to always do it. working on it. hang in there.