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!”