Out of the mouth of babes? An anecdote from Brian Tanswell at Weobley:
On Sunday, at the end of Mass, my five-year-old granddaughter,
Sophie, tugged at my hand.
“Grandad,” she said, “You must always say “amen” at the end of a prayer.”
“Oh yes,” I said. “Why’s that?”
She looked up seriously. “Because it’s like putting a stamp on a letter.
Without a stamp, the letter won’t go. And without “amen” the prayer
won’t go to Jesus. So you must NOT forget to say amen!”