People's impressions of the quality of their performances are often surprisingly inaccurate. In this paper, I discuss three specific factors that contribute to error in self-assessment. First, at a most basic level, individuals must possess a certain level of knowledge to simply distinguish weak from strong performances. Thus, a lack of skill can contribute to erroneous self-assessments. Second, even those who possess skill might rely on the wrong information to evaluate their performances. I discuss how relying on preexisting self-views can lead estimates of one's performance astray. Third, I discuss how motivational forces can play an indirect role in overconfidence. In particular, theories of intelligence that inspire people to think well of themselves also inspire behaviors that contribute to overconfident impressions of how well one has performed on a task. Finally, I discuss how we can draw on this research to improve accuracy in self-assessments.