The key to playing hockey at a high level is to not think. 

The reason systems exist is so that everyone is in the right place at the right time so that decision-making is kept to an absolute minimum. Coaches are trying to instill in their players a cell-level reaction to every action on the ice; If A happens, you do X. If B happens, you do Y. 

Obviously, individual skill has an effect on the outcomes of what happens at the end of those reactions, but when you get players where they all expect one another to be, the impact really adds up.{{