When I am talking with my kids I know I have got it right when one of them says “truth” to a statement I make. They simply mean that they agree, that it resonates with them. It does not have to be a scientifically proven fact, it is just something which they can stand behind.
One translation of the word Amen is “truth”. We say it when we hear something which we feel we agree with, which we can feel ourselves to be a part of, which we are invested in. It is an energetic statement, joining in with what has been said. Totally, absolutely, definitely, yes!
When there is an Amen at the end of a prayer in Church it is there on purpose. It is an invitation for you to say, “Yes, I am on board with this”. Jesus gave us the Eucharist? Yes! God blesses us? Yes! Amen! Amen!
Sometimes we do not want to say Amen at the end of something - that is fine. Other times, though, we just kind of forget about it, and that is missing a chance to affirm something wonderful and life giving.
I once had a colleague who said that if the people did not say Amen at the end of the Eucharistic Prayer or after the Blessing it wouldn’t work. I prefer to think God is a bit bigger than that. Of course God always does God’s stuff. When we respond enthusiastically with a loud “Amen” we are throwing ourselves right into the middle of all that grace and blessing instead of tentatively dipping a toe in the edge, or even wandering off in the opposite direction.