Vedanta says you cannot go into waking or dreaming without traversing through the corridor of deep sleep. The dreamer disappears first into deep sleep and from there becomes the waker, he writes. But even in a dream state, "you are not safe because it is a state" These states come and go; you are not safe until you realize yourself as 'this'
Swami Sarvapriyananda teaches one of the shortest and most profound upanishads accompanied by Gaudapada's Karika. This lecture covers Mantra 5-6.