You needn't be nervous. All you have to remember is to be sincere.
6 seconds sound clip from the Meet John Doe (1941) movie soundboard.
You can hear this line at 00:40:42 in the DVD version of the movie.
Quote context
[...]
- Okay, Beany, that's enough. Alright, scram now.
- John, here's the speech. It's in caps and double spaced. You'll have no trouble reading it.
- Not nervous, are you? Of course not, he wouldn't be.
- Who?
- Don't let your knees rattle. It picks up on the mike.
- You needn't be nervous. All you have to remember is to be sincere.
- Pick up that phone, it's for you. Okay.
- Hello? Yes, mother. Thank you, darling.
- There he is, the poor dear man.
- Good luck to you, Mr. Doe. We are all for you.
[...]