I think it's healthy for a person to be nervous. It means you care - that you work hard and want to give a great performance. You just have to channel that nervous energy into the show.
If someone really takes a risk, it doesn't get dismissed. That's what happened when the Oscar was won posthumously by Heath Ledger, who did one of the definitive villain performances of all time. But it really has to be exceptional in defining everything we previously knew about the actress or the actor.
