I gave this speaking advice to a friend who spoke at a reception in honor of her boss. Even though your circumstances might be different, you can apply the truths behind what I am saying to almost anything you do.
"Peace and calmness and self respect and pride be with you as you give your tribute to Andy tonight. Remember...you represent him tonight. You are his ambassador. Be proud.
Own the room with an inner authority borrowed from him. Have a glass of water ready. Under stress our mouths get dry. Look around the room. Pick out a friend and look at them when you get nervous. Save any insecurity or feeling of inferiority for much later when you are back home.
Tonight is mainly about Andy but it is also about you who had enough drive and brains to be his assistant for years. Don't disparage his choice. You are the ambassador tonight of one of the greatest men who ever lived."
I know you don’t need this broken down, but just in case you didn't t have time to think about it...
Who do you represent?
How do you prep for a presentation?
How do you lower your anxiety?
You can always have a breakdown later.