For the first degree of this virtue, take care, Philothea, not to admit any sort of carnal gratification that is prohibited and forbidden, as are all those which are taken out of marriage, or even in marriage when they are taken against the rule of marriage. For the second, refrain yourself as far as possible from useless and superfluous delectations, though they be lawful and permissible. For the third do not set your affections on those pleasures and gratifications which are commanded and ordained; for though we must practise certain necessary delectations—that is to say, those which concern the end and institution of holy marriage—yet we must never set our heart and mind upon them.
— Chapter XII, Of the Necessity of Chastity, St. Francis de Sales, Introduction to the Devout Life