In dream you are distinct from the physical body. In deep sleep, you are distinct from the body and the mind. You enjoy peace and bliss in deep sleep. This proves that you are neither body nor mind, but you are All-Blissful Soul
From Amrita Gita by Swami Sivananda, copyright The Divine Life Society. Swami Sivananda was a self-realized Master and a very practical Guru. Following His teachings can lead you to the Absolute.