During our football season, whenever we were down by a lot at halftime our coach would tell us, "You're getting outwanted. They have more will to win than you do."
Any competitor wants to win. But our coach did have a point in that some want it more than others. They tend to play harder because of their will to win. One reason desire is so important is that it motivates us in everything we do. A player can try and try to force himself to give outstanding effort, but he won't be able to keep it up for long unless the final goal of winning motivates him.