This paper aims to show that widespread, serious errors in the self-assessment of affect are a genuine possibility—one worth taking very seriously. For we are subject to a variety of errors concerning the character of our present and past affective states, or “affective ignorance.” For example, some affects, particularly moods, can greatly affect the quality of our experience even when we are unable to discern them. I note several implications of these arguments. First, we may be less competent pursuers of happiness than is commonly believed, raising difficult questions for political thought. Second, some of the errors discussed ramify for our understanding of consciousness, including Ned Block's controversial distinction between access consciousness and phenomenal consciousness. Third, empirical results based on self-reports about affect may be systematically misleading in certain ways.