In a context marked by negative health indicators that make structural aspects more salient, this paper aimed at understanding and explaining the processes and determinants at work that positively and negatively interfere with the professionals' health in the French public nursing home environment. To this purpose, the qualitative approach by grounded theory was chosen. In total, 90 semi-structured interviews were recorded and 43 were transcribed; in addition, 10 observations of 46 participations in meetings and working groups were carried out in four public service and hospital establishments. Our results indicate that the role of health workers, its definition, and its execution are fundamental to the understanding of their health at work. Two protective and constructive processes are involved in the maintenance and development of the professionals' health in this work, with considerable confrontations with death and suffering: individual and collective control of emotional and cognitive commitment, and the development of resources for formation, information, and cooperation. Nonetheless, they are jeopardized when a lasting imbalance is generated between the work's demands and the available resources. This leads to a loss spiral in organizational, inter-individual, and individual resources that makes it difficult to sustain work.