The underlying emotion that governs all the activity in the ego is fear. The fear of being nobody, the fear of nonexistence, the fear of death. All its activities are ultimately designed to eliminate this fear, but the most the ego can ever do is to cover it up temporarily with an intimate relationship, a new possession, or winning at this or that. Illusion will never satisfy you. Only the truth of who you are, if realized, will set you free. Why fear? Because the ego arises by identification with form, and deep down it knows that no forms are permanent, that they are all fleeting. So there is always a sense of insecurity around the ego even if on the outside it appears confident.

Eckhart Tolle

from A New Earth: Awakening to Your Life's Purpose