It may sound contradictory, but most people who are proud actually suffer from low-self esteem. They are constantly insecure, afraid, or feel unworthy, hence the need to oversell their worth.  People who have felt small, overlooked, unloved, or powerless in the past are more likely to develop a superiority complex. That constant desire to be seen, praised, and respected at all times usually stems from a deep place of hurt or the fear of being vulnerable.