John has practiced his difficult trumpet solo over and over before his performance. He has played it perfectly in his practice room. However, when he performs in public, he makes mistakes due to his anxiety. John is a victim of .

Social impairment

Explanation:

Social impairment: In psychology, the term "social impairment" is described as a phenomenon that occurs when a person performs worse or behaves in a less "positive way" when he or she is surrounded with other persons. While performing a specific task an individual would perform it better when he or she is alone instead of being in a crowd and there is often a chance of making mistakes as the person might feel anxious.

In the question above, John is a victim of social impairment.