I could see being so nervous/overwhelmed/scared/in-awe/whatever that you have "performance problems" in real life.  But Bruce Willis refused to shoot a movie sex scene with Ms. Berry for other reasons:

Willis said: "I get all awkward. She's beautiful. It's almost like looking at an eclipse of the sun.

"You have to poke a pin through a card and look at her through that. She's so stunning you could damage your retina."

If that was the problem then I think I would just close my eyes and try to manage using Braille or something.