Maybe this is why they're called "the small hours": Bed time is very contained time. You, either alone or with a partner, under sheets and pillow-rested, not going anywhere. Your body doing less for (one hopes) several hours; your mind doing its sleep thing, which can expand to whatever -- dreaming, thinking at different levels of concentration and consciousness -- but if you're going anywhere physically, it's not under your own power. It's as if you're cocooned. And you're with yourself. It's an especially pure way of being with yourself.