The world is the creation of your mind; go into deep sleep; it is negated! That is why sleep is said to be a form of Samadhi, when the dhi (intellect) becomes sama (balanced), merged in equanimity. (SSS Vol. 10, p. 88)

Deep sleep is often compared to samadhi, for, the senses, the mind, the reason, are all absent therein; only the ego is immersed in itself. It is in bliss, but, it is not aware of that bliss, for, waking alone gives that knowledge. So, what can grant Realisation is the awareness of the waking stage and the bliss of the sleeping stage. Concentrate on the point, where one is having these two: that is the moment of victory.

In the deep sleep stage, the senses do not work; one is immersed in the I consciousness only; that is to say, one is in Samadhi, (the state of bliss). Only, one is not aware of it, at the time. There is just a trace of ignorance. During the waking stage, there is knowledge, but no Ananda (bliss). In deep sleep, there is Ananda, but, no knowledge. That is why it is said, liberation is attained the moment one is able to fix himself at the point where there is the experience of both jagrat and sushupti (waking and deep sleep).

In deep sleep, you are one with yourself, though at the time you have no Citta and no Ananda. The realisation that you are not two but One will endow you with the awareness and the bliss. (SSS Vol.11, pp. 15, 48, 99)

(See – Four States)