I don't doubt that confidence, mind control, belief, etc. contribute in some way to success in anything, but it's wrong to overstate their importance.
If you don't understand the rules of the game, how to make a decent entry, how to hold a position, how to set appropriate stops, etc. then no amount of self belief will help you. You can only develop these skills through practice and learning from your mistakes.
Perspiration not inspiration is more reliable for earthlings.