We see how the husbandmen have a method for separating the chaff, which is united with the wheat, with a view to employ each for its proper purpose, the one for the sustenance of man, the other for burning and the feeding of animals. The labourer in the field of temperance will in like manner distinguish the satisfaction from the mere delight, and will fling this latter nature to savages “whose end is to be burned,” as the Apostle says, but will take the other, in proportion to the actual need, with thankfulness.
Many, however, slide into the very opposite kind of excess, and unconsciously to themselves, in their over-preciseness, laboriously thwart their own design; they let their soul fall down the other side from the heights of Divine elevation to the level of dull thoughts and occupations, where their minds are so bent upon regulations which merely affect the body, that they can no longer walk in their heavenly freedom and gaze above; their only inclination is to this tormenting and afflicting of the flesh.
It would be well, then, to give this also careful thought, so as to be equally on our guard against either over-amount, neither stifling the mind beneath the wound of the flesh, nor, on the other hand, by gratuitously inflicted weakenings sapping and lowering the powers, so that it can have no thought but of the body's pain; and let every one remember that wise precept, which warns us from turning to the right hand or to the left. I have heard a certain physician of my acquaintance, in the course of explaining the secrets of his art, say that our body consists of four elements, not of the same species, but disposed to be conflicting: yet the hot penetrated the cold, and an equally unexpected union of the wet and the dry took place, the contradictories of each pair being brought into contact by their relationship to the intervening pair.
He added an extremely subtle explanation of this account of his studies in nature. Each of these elements was in its essence diametrically opposed to its contradictory; but then it had two other qualities lying on each side of it, and by virtue of its kinship with them it came into contact with its contradictory; for example, the cold and the hot each unite with the wet, or the dry; and again, the wet and the dry each unite with the hot, or the cold: and so this sameness of quality, when it manifests itself in contradictories, is itself the agent which affects the union of those contradictories.
What business of mine, however, is it to explain exactly the details of this change from this mutual separation and repugnance of nature, to this mutual union through the medium of kindred qualities, except for the purpose for which we mentioned it? And that purpose was to add that the author of this analysis of the body's constitution advised that all possible care be taken to preserve a balance between these properties, for that in fact health consisted in not letting any one of them gain the mastery within us.
If his doctrine has truth in it, then, for our health's continuance, we must secure such a habit, and by no irregularity of diet produce either an excess or a defect in any member of these our constituent elements. The chariot-master, if the young horses which he has to drive will not work well together, does not urge a fast one with the whip, and rein in a slow one; nor, again, does he let a horse that shies in the traces or is hard-mouthed gallop his own way to the confusion of orderly driving; but he quickens the pace of the first, checks the second, reaches the third with cuts of his whip, till he has made them all breathe evenly together in a straight career.
Now our mind in like manner holds in its grasp the reins of this chariot of the body; and in that capacity it will not devise, in the time of youth, when heat of temperament is abundant, ways of heightening that fever; nor will it multiply the cooling and the thinning things when the body is already chilled by illness or by time; and in the case of all these physical qualities it will be guided by the Scripture, so as actually to realize it: “He that gathered much had nothing over; and he that had gathered little had no lack.”
It will curtail immoderate lengths in either direction, and so will be careful to replenish where there is much lack. The inefficiency of the body from either cause will be that which it guards against; it will train the flesh, neither making it wild and ungovernable by excessive pampering, nor sickly and unstrung and nerveless for the required work by immoderate mortification. That is temperance's highest aim; it looks not to the afflicting of the body, but to the peaceful action of the soul's functions.
Source: On Virginity (New Advent)