Cognition, motivation, and emotions are recognized by psychologists as the three fundamental classes of mental operations, yet most research in educational psychology has focused on the first two classes. Educational psychology textbooks for preservice teachers contain chapters on learning, problem solving, assessment, and motivation, but not on emotions. One reason for this is the "suspicion in Western culture that there is something wrong with emotions". Emotions are often thought of as out of control, destructive, and primitive rather than thoughtful, civilized, and adult. In contrast, recent research has shown that emotions are an essential part of a productive adult life and are important in understanding the goals preservice teachers attain. In this article, the author presents an overview of current research on emotions, and discusses teachers' positive emotions and evidence that expression of positive emotions helps teachers' effectiveness. She also discusses teachers' negative emotions and strategies teachers can use to reduce their negative emotions. (Contains 1 note.)