Everyone is overly critical of their performance. I recently did South Pacific and the woman who played Bloody Mary is one of the most talented people I have ever had the honor of sharing a stage with. At the cast party we watched a tape of the show and the whole time she was saying "Oh my god why did they give me this part they should fire me right now" It's also a good idea to watch the tape AFTER the show ends because then you stand on stage and think about what you did on the tape.
If you truly love acting just do it and when you have confidence in yourself it shows in your performance.
"I'll show you a laughgasm. I'll gasm all over this stage!"
"Interesting choice"