There are some things whose value is only understood when they are gone, like an umbrella. We don't think of a protective wing to shield us from the rain or a shade to keep us warm in the sun. At the very beginning of a deep conversation, we forget we're sitting under that umbrella. We don't even realize how much we appreciate a delicious meal in the cool shade of the room.

Then there are things that enhance the comfort of life. Once we realize their value, they become indispensable.