Ego

See Also in Wikipedia :

   1. The self, especially as distinct from the world and other selves.
   2. In psychoanalysis, the division of the psyche that is conscious, most immediately controls thought and behavior, and is most in touch with external reality.
3.
   a. Anexaggerated sense of self-importance; conceit.
   b. Appropriate pride in oneself; self-esteem.

      1. the self of an individual person; the conscious subject
      2. (Psychoanalysis) the conscious mind, based on perception of the environment from birth onwards: responsible for modifying the antisocial instincts of the id and itself modified by the conscience (superego)
      3. one's image of oneself; morale to boost one's ego
      4. egotism; conceit

Source

www.thefreedictionary.com