Positive thinking gives you an edge every time a person is gambling. Base on my experience, every time that you have doubts on your card, no matter how strong it is, you will end up losing the game because you are not confident. Especially in the game of poker, the other player will definitely feel that you are bluffing if you're not confident. You are also willing to take the risk if you are thinking positive, the more you try, the more chances of winning.
I don't know mate, but your positive thinking will not change the outcome of the game. If you are not confident then don't bet on it simple as that.
We all know for a fact that everything is based on luck, and even if you are not that confident but decided to bet and won, what do you think influence the outcome then? Luck or Confidence?