Seriously mentally ill patients' unusual behavior is considered challenging in caring relationships, but we know little about how this affects mental health nurses' vulnerability. This article uses a phenomenological design inspired by Heidegger's philosophy with the results of fieldwork and reflection groups with 11 nurses on an acute ward. The nurses were exposed to an accumulation of negative emotions, caused by potentially or actually harmful scenarios that were more extreme than those in other nursing contexts. They protected themselves through limit-setting approaches, which conflicted with their standards of building trusting relationships with patients. The feeling of guilt might function as an appeal for authentic practice, but a change in practice requires the use of acknowledgment approaches and the systematic debriefing of accumulated burdensome feelings.