What's going on that a highly skilled athlete can suddenly and inexplicably lose the fundamentals of fielding? The usual explanation is that these players start to "overthink" their automatic, highly tuned visual and motor skills, and sabotage them in the process. But this has never been proven, nor is it clear just what this means on a basic cognitive level.
Being put on the spot to display one's knowledge or skills can feel terribly uncomfortable and scary. The key to overcoming these emotions is to be prepared and recognize that our fears stem, not from a lack of self-worth, but quite the opposite. Our fears are born out of a deep sense of love for the self that wants nothing more than to protect us and keep us safe.