Dear Faldage: No wonder you don't get any milk.

A sample definition:

Fanaticism [Lat. fanaticus, inspired]: Ger. Fanatismus; Fr. fanatisme; Ital. fanatismo. The word anglicized as fanaticism
was used in classical times of priests who were supposed to be the intermediaries of revelations or of oracles; in particular, it
was applied to those of them whose actions were wild or noisy. The word has now come to be used in a disparaging sense.
We say that, in the middle ages, extreme ascetic practices, such as scourging, branding, and the like, were products of
fanaticism. The term implies credulity in religious or other matters, accompanied by a vehemence which expresses itself in
hatred or violence towards opponents.

Reader's Digest long ago had definition: A fanatic is one who redoubles his efforts when he realizes he has lost sight of his goal.