By sleep we understand the covering of ourselves from the world of which we are conscious, but we do not realize that, when we are awake, we are covering ourselves from another world which, in fact, is more real; it is the self which is covered. The difference between the sleeping and the waking state is that, when we cover ourselves from what, in fact, is real, we say, "I am awake" and, when we cover ourselves from what is unreal and illusion, we say we are asleep.