Let him lead the conversation. All you have to do is smile and nod. Whatever he is planning to talk about doesn't require an immediate response. If he brings up something and expects an immediate response, tell him you will get back to him on that.
Don't bludgeon an ant with a sledgehammer. Just wait to see what this is about. Whatever it is, you can hAndle it! Really! You can do it. Be calm.
"You know, it's times like these when I realize what a superhero I am." Tony Stark/Iron Man
“Focus on what you can do, then do it with all your heart.” Lois Wilson