To be fair, believe in yourself is commonly a proposition driven by ignorance (specifically of your personal capabilities). In softball, any kid can, once in a while, hit a screaming line drive (and man it feels awesome when it happens that first time by chance), but it takes a bit of practice and dedication to hit that screaming line drive commonly.

There’s actually a process we watch in Street Fighter in which a novice player will notice they can Hadouken (throw a fireball) once in a while. Then they learn the actual maneuver. Then they practice until they can do it routinely. Then they figure out the best circumstances to Hadouken the enemy (so it will not be blocked or repelled and to maximize effectiveness.) At that point, the player has a pretty solid awareness of their Hadouken skill that has been tested, and is visible to peers.

This is why chess enthusiasts get a ranking, which means learning how to get ranked and compute a ranking. Believing in yourself isn’t going to win you games against top Russian chess guns. But if you play the game a whole bunch, get ranked, understand the theory and the dynamics of the pieces on the board, then you won’t need to believe in yourself since you’ll know from experience what you can do.