I do that every day at work!
It was even capitalized on by Anthony Robbins in his Personal Power tapes.
The principle involved is that MIND FOLLOWS MATTER, in a sense.
Another way of saying that is that MENTAL FOLLOWS PHYSICAL.
Actually it is a two way street.
Anything that causes mental anguish, causes physical illness.
But the physical can influence the mental as well.
If you are depressed, it is because you allowed yourself to get physically depressed and that keeps you emotionally depressed.
See someone with a 'SAD LOOK' on their face? Probably are sad, huh?
Take that person, have them sit up straight, have them smile, etc. and soon they will not feel sad. I.E. Forcing a change in the physical causes a corresponding change in the mental.