In the case of football that might actually be a good lesson: save enough energy for the end of the game so that you can play best when the other team is tired. Of course you need to play the whole game, but if you play all but the last 5 minutes working just hard enough to keep a tie game, then you can pull ahead in the end.

This only works in time limited sports though. Most real world situations are not time limited like that and so the advice doesn't apply.