MT - once you did it do it again.
You won't experience it every time but often you will experience people changing their opinion about you (which obviously wasn't good enough up to then) and you will also experience changing your own opinion about some people (which ... see above) WHILE SINGING. As I did.
It helps to be good. But it isn't really necessary, just look at some of those megastars. You should only avoid to give them the impression that you want to pull their legs.
From this point of view there is no need for courage, nor is there any reason for stagefright.