After yesterday's sermon -- in which we considered King David's evening prayer in Psalm 4 -- someone in the church family pointed me to a beautiful little piece by John Piper, dealing with the same themes: "A Brief Theology of Sleep."
The middle paragraph (of five) says this:
Why did God imagine sleep? He never sleeps! He thought the idea up out of nothing. He thought it up for his earthly creatures. Why! Psalm 127:2 says, “It is in vain that you rise up early and go late to rest, eating the bread of anxious toil; for he gives to his beloved in his sleep.” According to this text sleep is a gift of love, and the gift is often spurned by anxious toil. Peaceful sleep is the opposite of anxiety. God does not want his children to be anxious, but to trust him. Therefore I conclude that God made sleep as a continual reminder that we should not be anxious but should rest in him.
I commend the whole little piece to you, which can be found HERE.