I buy that as a general statement about most things in life. Confidence in one's ability translates into smooth performance.
However, when the game is no longer the game and it becomes something else then competitive anxiety creeps in. Taken to its logical conclusion it is something like this. Let's say you have the rent money on the line and have already lost the food money. If you lose your wife's depression and the possibility that you could "lose everything" including her has an effect on how you play. Of course this is an exaggeration but minor variations have an effect as well.
However, when the game is no longer the game and it becomes something else then competitive anxiety creeps in. Taken to its logical conclusion it is something like this. Let's say you have the rent money on the line and have already lost the food money. If you lose your wife's depression and the possibility that you could "lose everything" including her has an effect on how you play. Of course this is an exaggeration but minor variations have an effect as well.