Esoteric Lesson
They cause our astral body to vibrate in a certain way, but this vibration was already placed there by higher beings. So anyone who never thinks in a non-sensory way will never bring new formations into the astral body. What happens in the astral body has an effect on the etheric body, but the etheric body is predisposed to receive new thoughts and forms. The old forms have a destructive effect on it and, from there, also on the physical strands of our nervous system. All of this must then be restored during sleep. The astral body is then temporarily connected to the higher hierarchies and thereby receives strength; the etheric body is separated from the astral body and is thereby regenerated. Without sleep, human beings could not live for long.
Cite:
GA 266b/1911-01-17/p007 · edition English