Have you been with a child the entire day and then have them fall asleep? They go from crazed to peaceful in a matter of humming seconds. They drift slowly and crawl into a comfortable space and relax. Then they push out their lips and ball up their fist and sleep.
At first you tiptoe around them to avoid waking them up. But slowly but surely you watch them. Their soft small body balled up and warm. They level of comfort they achieve is magnificent.