Attribution Theory:

Attribution theory is why we blame our own or someone’s behavior on reasons either internal (dispositional — personality factors/traits) or external (situational — environmental factors). Bias can overemphasize internal factors in explaining other’s behavior, even when situational factors are more relevant. Another bias is protecting our self-esteem by attributing our successes to dispositional factors (we are great) and failures to external factors (it was not our fault). Also see: Covariation Model and Reward