"In this article, we analyze relationships between a change in feelings and the development of the ‘power to act’ during a clinical intervention with occupational-health physicians. We describe the case of an occupational physician, whose feelings of personal inefficacy and uselessness were transformed during the intervention. Although the physician was initially affected, embarrassed, and taken aback by the analysis of her activity, this destabilization was productive in that it led her to discuss the goals of her actions with her colleagues, and to reflect upon the relationships between the goals and motives of the activity. We outline a sequence from a dialogue between the physician and one of her colleagues, in which we analyze the emotions and the arguments exchanged. We conclude that the affect that was initially responsible for the embarrassment of the physician, cleared the path for a new way to see, imagine, and act. Based on this analysis, we can: 1) distinguish between affect, emotion, and feeling: emotion and feeling are instruments of affect; 2) delineate two necessary conditions for the transformation of feelings: the perception of an affect and the enhancement of meanings; 3) demonstrate a link between a change in feelings and the development of the power to act.