Answer:
Performance anxiety is usually caused by fear of failure or not being good enough. One way to help someone is to ask them what they're scared of failing. Failure is objective; it means different things to different people. For example, 2 athletes can have performance anxiety, but for two different reasons. The first one is scared of losing. The second one can be scared of not being a star athlete.
If people will categorize you based on your fails, then its on them and not you. Telling a person with performance anxiety that failure does not define them often helps. Success is not erased by failures.