Deep sleep brings on a sense of nondual peace with it. This experience one gets only in the absence of mind. When one focuses his attention consciously on the formless witness of the three states then which wards of the mind/duality/illusion [waking or dream].
So, one gets to the real nature of the soul or consciousness by focusing the attention on the formless witness, consciously and at the same time by being aware of the body and the universe and no them consciously as consciousness alone.
Once one becomes fully aware of the fact that whatever exists as object [body + universe] with form or shape are also consciousness because they are made of consciousness.
Thus, deep sleep illustration can be utilized the real nature of the soul/consciousness, which is without duality [forms and shapes]. Thus remaining in duality becoming aware of soul/ consciousness is the truth true self is Self-Realization.
