In our world, when we fall asleep, we, in essence, lose awareness, disconnect from the world, from life. We enter a state of being detached from life, and are left only with so called a level of minimal life in us when, in essence, we are not sure whether (if we can ask it this way) we will rise after sleep or not. So why do we rise? All of a sudden, we receive some awakening from within, and then we wake up and again continue our life on a new day.
But this state in which we disconnect from reality and enter into dreams is very special. Similar states exist in the spiritual as well, and this is because everything that exists in the corporeal is the result of the spiritual.