I think anxiety is related to perception and sensitivity.
I have pretty severe anxiety when it comes to certain things. I've gone through times (and still have times) when I have anxiety about everything.
It's just basically thinking of possibilities and worst-case scenarios... and since I have a vivid imagination, it overtakes me.
I think the way to defeat anxiety is to be active. I think anxiety is also excess energy. When you start shaking, have a panic attack, or faint, it's because you are trying to be normal. Look at Gilbert Gottfried who obviously has tons of excess anxious energy:
You can say he's always moving and rubbing his hands together. Sometimes, doing stuff like that can help anxiety. With a player like White, during the game anxiety wouldn't be a problem... it would be in real life.