I hear you, Mark. Some book I read -- they all kind of blend together now into one massive self-help 16-ton Monty Python weight dropping from the ceiling -- said that you should visualize a STOP sign whenever you start having those thoughts. They take you down dark scary lanes you don't want to visit even in the daytime.
For myself, I try to imagine Liverpool. LOL. No, really. I went to Liverpool in 1985. A bad, bad place at that time -- hooligans were setting the upper decks of the buses alight, smashing in the windows of the few shops still open.
I wandered out of a pub one night and took a left instead of a right.
A bad, bad, bad decision.
So now, when I start going down those awful lanes of the mind, I cast back to that night, too full of lager by half, wondering where on earth my hotel was, and hearing this Scouser git demand to know wot oi fought oi was duin 'round 'ere. I remember the echo of his voice along the brick walls shortly before he and his mates introduced my face to their bovver boots.
And I think to myself -- hey, SP -- take a look around. Stop.