Maimonedes Guide I:34, p. 77: one whose testicles have a hot and humid temperament ... in whom the seminal vessels abundantly generate semen ... it is unlikely that such a man, even if he subject his soul to the most severe training, should be chaste.

Nonetheless, in the Code, [Hilchot De-ot 3:2, 3; 4:19] Maimonides spoke of the need of self-control, indicated sanctions, [Hilchot Ishut I:4, 5] and gave the refraining from an illicit sexual liaison as the very model of repentance. (You remember the case: the same woman, same town, same desire. If you don't, that is true repentance ... [Hilchot Teshuva II:1])