keberoxu, in the wonderful Master and Commander there's a lovely phrase describing obsessive depression. I quote (one character - obviously based on the ill-fated Lord Edward Fitzgerald if he had escaped the ethnic cleansing that followed the 1798 Rising - is telling another that he has deliberately failed to hand up someone else to the hangman, but it looked as if he did this in response to blackmail; the character quoted below is replying to him, and talking about how he's dwelling on this angrily):

"But you had not: it is a sick fancy. Indeed it is not far from morose delectation: take great care of that sin, James, I beg."

Morose delectation! What a wonderful description of how we can dwell on shame and anger and sadness and guilt, sometimes for months or years!

As for changing the subject, that's what we do when we're prepared, but I'm always reminded of the time I convinced myself I was going to be gentle-natured and mannerly on the road, I would model myself on my dearest friend, whose whole life is dedicated to her relations with others, and who seriously studies this through meditation retreats and careful, caring strategies. I was happily enjoying a fantasy of perfect balance and forgiveness when, as I cycled through a green light, a powerful-looking white-haired man flew across, turning in front of me while blaring his horn - and I immediately and without conscious thought gave him the bird. *Pouff* went my fantasies of gentlewomanliness!