Competition is no different. When we reach the pinnacle of the mountain, there is always a target on our back. For teams that win championships, that target is known as "next year." The defending champions have a very small amount of time to enjoy their championship before they have to defend it. So our self-esteem might go up when we win, but it doesn't last long because we have to validate it again through the next competition.
Why, then, do we attach self-esteem to competition if we know that there will be a dip in it when the next season starts? Why do we allow our self-esteem to go up when we win if we know we have to defend it from going down again?