The ego is always on guard against any kind of perceived diminishment. Automatic ego-repair mechanisms come into effect to restore the mental form of "me." When someone blames or criticizes me, that to the ego is a diminishment of self, and it will immediately attempt to repair its diminished sense of self through self-justification, defense, or blaming.

Eckhart Tolle

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