For example athletes whose entire self worth comes from their performance in their sport. When you define yourself based on your performance and believe your worth is based in that performance you are setting yourself up for devastation later. We all saw it in Urban Meyer after the infamous Alabama loss. I think this pressure also plays a role in the Simone Biles situation.

Humans cannot base their self worth on a singular thing, because eventually that singular thing will fail. I can see how mental illness creeps in and has such a prominent effect when we place that much pressure on ourselves.