Being fed up with something is a prevalent and fundamental human experience. Although the relevance of mental satiation, that is, the process of becoming fed up with an action, is highly acknowledged in organizational psychology, almost no empirical research has examined this concept. In this article, we take a social cognitive neuroscience approach to mental satiation. By building on and extending the classic work of Lewin and Karsten, we propose a new model of mental satiation that focuses on the cognitive, motivational, and neural processes underlying mental satiation. Our model starts with the assumption that repeated performance of an action undermines one's need for competence and hence leads to a loss of intrinsic motivation. We then distinguish between two phases of the satiation process: The first phase is characterized by a loss of intrinsic motivation to perform the action. The second phase starts when the intrinsic motivation has vanished and volitional control is required to continue the action. We predict that the loss of intrinsic motivation in the first phase of the satiation process is correlated with a decrease in activity in brain regions associated with positive hedonic experience, such as the nucleus accumbens, the ventral pallidum, and the medial orbitofrontal cortex. In contrast, the growing aversion toward the action during the second phase of the satiation process is predicted to be correlated with an increase in activity in brain regions associated with unpleasant affect and volitional control, such as the amygdala, the anterior insula, and the anterior cingulate cortex.