the actual physiological cause of ressentiment, vengefulness, and the like: a desire to deaden pain by means of affects… “Someone or other must be to blame for my feeling ill”—this kind of reasoning is common to all the sick
Nietzsche grounds ressentiment not in reactive self-defense but in the physiology of chronic suffering, identifying the compulsion to assign blame as its psychological mechanism.
, On the Genealogy of Morals, 1887thesis