I can't say enough about how much I LOVE this video.
Opera singer (international superstar!) Joyce DiDonato hosts a Q&A session after giving a masterclass at Juilliard for young singers aspiring to have performance careers. The entire video is full of exceptional insight, but my favorite is her description of the critical inner voice (our internal monologue that constantly speaks even when we're performing). Not only does she explain it, but she talks about how to fight it.