I know that speaking positive thoughts out loud can change my life

There's a strange shrinkage that happens when a thought leaves your mouth. The disaster you rehearsed for three hours at night comes out over coffee in about nine seconds, and both of you notice how small it sounded.

Something in the head is not required to be coherent. Out loud, it has to hold a shape, get to the end, survive somebody's face. Most of the worst ones can't.

The reverse is also available and gets used far less. Say the good assessment of yourself aloud — flatly, in an ordinary voice, in the car — and listen to whether it holds up. Often it does, and you've never once given it the chance.