A few of St. Augustine's sermons on Lent have come down to us. This is a translation published in 1959 - you want sermons 205-211, that start on p. 185. I am not sure of the dating or specific context - they seem to have been preached in different years, since the themes carry over from sermon to sermon - such as the repeated reminder that if you abstain from some food or drink, it then makes no sense to replace what you have sacrifice with something that either is more costly or affords you as much or greater pleasure.
I appreciated this, from Sermon 207.
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Of course, care must be taken to avoid merely changing instead of lessening pleasures. For you may observe that certain persons seek out rare liquors in place of their ordinary wine; that they, with much greater relish, counterbalance by the juice of other fruits what they lose by denying themselves the juice of grapes; that, in place of meat, they procure food of manifold variety and appeal; that they store up,
as opportune for this season, delights which they would be ashamed to indulge in at other times. In this way, the observance of Lent becomes, not the curbing of old passions, but an opportunity for new pleasures. Take measures in advance, my brethren, with as much diligence as possible, to prevent these attitudes from creeping upon you. Let frugality be joined to fasting. As surfeiting the stomach is to be censured, so stimulants of the appetite must be eliminated. It is not that certain kinds of food are to be detested, but that bodily pleasure is to be checked. Esau was censured, not for having desired a fat calf or plump birds, but for having coveted a dish of pottage. 5 And holy King David repented of having excessively desired water. 6 Hence, not by delicacies obtained with much labor and at great expense, but by the cheaper food found within reach, is the body to be refreshed, or, rather, sustained in its fasting.
