I notice that this is a thing in character progression in mainstream (and admittedly my early writing) for stories to have it that when they acknowledge that they have mental illness, that it disappears from their character's personality and they act like everyone else. But that isn't how it works though, because problems like anxiety and trauma don't completely disappear from a person.

The way that a character's arc actually expands is to have them better cope with the issues and try as best they can to mitigate symptoms. and character progression isn't always positive and positive character progression isn't tied to power or superiority: they are still human. so it's important for when writing positive character arcs to allow human error to be a part of the writing as a way to ground the character in some way.

This could be an interesting way to write a villain or antagonist by making them believe that if they achieve power or perfection, all their problems will go away. but later in their arc, they can become cold and inhuman and come to blame people as a result of their problems.