Everyone has the brain power to make money in stocks. Not everyone has the stomach.
There are reasons for why all sports teams have set plays and repeat these same plays over and over in practice. It is not about brainpower, but rather having the ability to follow a plan when things are either going right or wrong. There are rules, structure, discipline, and repetition that can all help to offset the fears from uncertainty. You don't have to be a tough guy or the smartest investment guy, just a disciplined individual who can enter or bail at the right time.
Good plans have to be robust enough to handle all situations and surprises. You don't have to always be right. Most good investors don't worry about the percentage of winning trades, but you do have to have plans for minimizing the pain of losses. We have often dwelled on these topics for the simple reasons that they are very relevant. Charlie Ellis has called investing a "loser's game" because success is all about making the fewest mistakes. The easiest mistakes to correct are those that involve bad behavior. They are in our control if we have the stomach to stay disciplined.