Waking, dreaming and deep sleep. Temporary and constantly changing states of mind. There is something that's ever-present and unchanging and the task at hand is to realize That Thou Art. Changing states of mind are but events or appearances within It as is the body and everything else, whether internal fabrications of mind or the external world gathered by the senses and reconstructed within mind.

That It's ever-present and unchanging implies It's not something to be achieved but just realized and with unwavering conviction. To "know" It and from an experiential, not intellectual perspective.