Did you ever come across this NYTimes interview by Jesse Green with Hugh Jackman before he ended his year-long run on The Boy From Oz?
Some excerpts :
"Q. Problems? Even at this point?
A. Absolutely. You know what's really weird? I actually got stage fright for the first time in my life six months into the run.
Q. Where from?
A. One night, during the song "Quiet, Please, There's a Lady on Stage," I cracked a little bit on a note. I forgot about it, but the next night when I came up to that note, about a line before, I sort of remembered, and then I really cracked on that note. I woke up the next morning and it was the first thought in my head. So I thought, "This is ridiculous," and forgot about it. That night, I was nervous all the way through Act I and then cracked badly. It was this feeling of humiliation onstage, where literally I would turn red and then get angry, and then I'd feel it underneath while playing the whole show. It started to envelop me, to the point where I'd wake up and I'd be nervous coming to the show. I've never had stage fright, I've never really understood it, but all day it felt like a Herculean effort to get out on the stage. I started thinking, "I don't know how to sing." And whatever used to happen naturally I was second-guessing. I wanted to vomit, all from a little note!
Q. Did you ever figure out what it was about?
A. No. But one day about a week later, thank God, this thought came into my head saying: "Even if you don't sing a note, just speak the words. This song has nothing to do with you. It's about Judy Garland." And I sang that night and I was just fine, and I literally felt like a demon was leaving my body. I looked down at Patrick (Vacariello) and he was just smiling, and I wanted to cry. "
Even the seemingly very experienced thespians get it once in a while