Chandogya Upanishad: ~ “Whoever sees the Self in all does not see death, disease, or diversity.

Bhagavad Gita: 7: 19:~ "Such a man who has attained knowledge of Atman. Atman is God in truth. Atman alone exists. Everything is Atman; there exists nothing except Atman. Such a man is extremely rare."

Bhagavad Gita Krishna says: ~It is only one amongst thousands of people who strive for spiritual salvation. Even amongst such seekers, it is only the rare person who gets to know the  Self correctly.’ (7.3)

The Self is not ‘you’, but the Self is the invisible Soul that witnesses the appearance and disappearance of the illusory world in which you exist. You are the false self (ego) within the false experience (waking).

You are bound by birth, life, and death, and form, time, and space, whereas the Self is birthless and deathless because it is a formless, timeless, and spaceless existence.

Thus, the Self is not limited to the waking state alone because it pervades everything and everywhere in all three states.

Thus, limiting the Self to a waking entity alone is the cause of ignorance.

The dream entity (dream you) and the dream world become falsehoods when the waking takes place. Similarly, the waking entity (you) and the waking world become falsehood when Advaitic wisdom dawns.

Advaitic Wisdom dawns when the waking entity (you) realizes it, itself is not the Self, but the ‘Self’ is that which witnesses the coming and going of the three states. The witness and the three states are one in essence. That essence is consciousness.

Consciousness is the ultimate truth or Brahman. Atman is second to none.

Thus, one has to know ‘What is mind?' ‘What is the substance of the mind?’ and ‘What is the source of the mind?’ to realize the non-dualistic or Advaitic truth.:~Santthosh Kumaar