Here's a quote from The Wee Free Men...
"She tried to pretend she hadn't thought that, but the was treacherously good at spotting when she was lying. That's the trouble with a brain -- it thinks more than you sometimes want it to."
Have you tried to have a lie down and tried NOT to think of a white elephant? Every time a thought comes in you think of an eraser going across your forehead, and then you try NOT to think of a white elephant again. It sounds weird, like "what is the sound of one hand clapping?", but it works much better.
Soon, I was able to do the eraser thingy and believe me the harder you try NOT to think of the white elephant, soon it Will be all you can think of.
Edit: Sometimes I "decorate" my white elephant up all pretty with paint too.
Aha! So, Bob's yer uncle... very clever.