People at the top of their game

For people at the top of their game. What makes them lose their edge?

Do they get tired of holding their spot at #1?
Do they forget why they were bent on getting to the top to begin with?
Do they realize it’s not as wonderful at the top as they originally thought?

Or maybe they forget to keep raising the bar at the top in the same way they kept raising the bar for themselves on the way to the top.