DEUT1694 [Among the fundamentals of repentance]: (9) The breaking of desire. One must impress upon himself that desire vitiate all deeds. He must withdraw from luxuries, even those which are permissible. He must follow the ways of separation and eat only to sate his soul and maintain his body. The same applies to his conjugal relations. For as long as a man follows desire, he is influenced by material considerations and is drawn away from the path of reason, at which juncture his evil inclination overpowers him, as it is written [this verse]: "When Yeshurun waxed fat, he kicked," and (Mishlei 30:9): "Lest I be full and deny and say, 'Who is Hashem?'" The desire which is implanted in a man's heart is the root of all his actions. He should, therefore, hasten to properly order his desire, as we have described at length above. And there is another great benefit in the breaking of desire, for through it one demonstrates that his heart is good and just and that he despises the physical nature which causes him to sin. And if one separates himself even from what is permissible, he therefore constructs a great fence against contact with the forbidden, reasoning: "If I do not fulfill my appetite with what is permitted, how, then, can I stretch forth my hand to that which is forbidden?"