What is this self Who am I?
Your real nature is stillness, light, expansion without center or periphery. It is unconditioned being, love. But you do not see it for you are a prisoner of your imagination and of second-hand information. You have enclosed yourself in a universe of concepts and beliefs. The ego is only a function, and to identify with it is a lack of true vision. Thoughts, feelings and actions appear in succession before the witness, leaving their imprint in your brain. Recalling them makes you believe in a continuity which is actually non-existent. But memory is a present thought, thoughts of the past occur in the present. In reality there is only presence, non-dual consciousness. We mistakenly take ourselves to be this or that, but there is only the true "I am" beyond time and space.
What is the real nature of the mistake I have made?
Desiring something which is nothing but an illusion, which has no foundation whatsoever; being afraid of truth, which is pure awareness free of thought.
Why would I be afraid of truth?
Because truth is life and you are afraid of living. You take yourself for an object which is born and dies, and you fear dying because you do not know life. It is only an object which is afraid and this object tries by all means to free itself. See that the effort to become free belongs to the belief in an object. The moment you see it turn your head and look behind.
~ Jean Klein