Good decision making often requires accurate predictions about how potential outcomes will make one feel. However, people often mispredict the emotional impact of unfamiliar circumstances. For example, they often overestimate the emotional impact that chronic illnesses and disability will have on their lives. In the present article, the authors look at possible sources of error in both the happiness reports of patients with chronic illness or disability and the happiness predictions of healthy people asked to imagine the same illnesses and disabilities. On balance, the available evidence suggests that, whereas patients misreport their well-being, healthy people also mispredict the emotional impact that chronic illness and disability will have on their lives.