Fear of not-being.
Why does one fear not-being? Because one doesn't know it? If one was not, which means if he actually dropped all preferences and attachments and was not anything, obviously there would be no fear.
The I is the fear.
UNITARY PERCEPTION. OBSERVATION WHICH INCLUDES THE OBSERVER AND THE OBSERVED AT THE SAME TIME. FREEDOM FROM ILLUSION. LIBERATION FROM THE HUMAN CONDITION.