When it comes to evaluating our own behaviour, we do the opposite (overestimate the impact of situational influences, and underestimate the impact of dispositional influences), may be due to the fact that we are unaware of others’ situational factors, and very aware of our own.
Example: when someone else performs poorly on a test, we tend to attribute the performance to intelligence (“he must not be very smart”). However, when we do poorly on a test, the attribution tends to become external (“the test was not fair”)