Back in 2005, Poker Hall of Famer Doyle Brunson published an article in which he discussed some "mind games" that work for him, and some that don't.
In the article, Brunson tells the story of a man named Keith who seemed to achieve great poker results by pumping himself up with confident, positive thinking before he sat down to a game. But after a while, that wasn't enough for him, so he decided to amp up the level of mental self-trickery.
"Then he decided that he'd play even better if he could convince himself he was losing a little in the beginning of a session," writes Brunson.