2 We must strive after a quiet mind. As well might the eye ascertain an object put before it while it is wandering restless up and down and sideways, without fixing a steady gaze upon it, as a mind, distracted by a thousand worldly cares, be able clearly to apprehend the truth. He who is not yet yoked in the bonds of matrimony is harassed by frenzied cravings, and rebellious impulses, and hopeless attachments; he who has found his mate is encompassed with his own tumult of cares; if he is childless, there is desire for children; has he children? Anxiety about their education, attention to his wife, care of his house, oversight of his servants, misfortunes in trade, quarrels with his neighbours, lawsuits, the risks of the merchant, the toil of the farmer. Each day, as it comes, darkens the soul in its own way; and night after night takes up the day's anxieties, and cheats the mind with illusions in accordance. Now one way of escaping all this is separation from the whole world; that is, not bodily separation, but the severance of the soul's sympathy with the body, and to live so without city, home, goods, society, possessions, means of life, business, engagements, human learning, that the heart may readily receive every impress of divine doctrine. Preparation of heart is the unlearning the prejudices of evil converse. It is the smoothing the waxen tablet before attempting to write on it.
Now solitude is of the greatest use for this purpose, inasmuch as it stills our passions, and gives room for principle to cut them out of the soul. [For just as animals are more easily controlled when they are stroked, lust and anger, fear and sorrow, the soul's deadly foes, are better brought under the control of reason, after being calmed by inaction, and where there is no continuous stimulation.] Let there then be such a place as ours, separate from intercourse with men, that the tenour of our exercises be not interrupted from without. Pious exercises nourish the soul with divine thoughts. What state can be more blessed than to imitate on earth the choruses of angels? To begin the day with prayer, and honour our Maker with hymns and songs? As the day brightens, to betake ourselves, with prayer attending on it throughout, to our labours, and to sweeten our work with hymns, as if with salt? Soothing hymns compose the mind to a cheerful and calm state. Quiet, then, as I have said, is the first step in our sanctification; the tongue purified from the gossip of the world; the eyes unexcited by fair colour or comely shape; the ear not relaxing the tone or mind by voluptuous songs, nor by that special mischief, the talk of light men and jesters. Thus the mind, saved from dissipation from without, and not through the senses thrown upon the world, falls back upon itself, and thereby ascends to the contemplation of God. [When that beauty shines about it, it even forgets its very nature; it is dragged down no more by thought of food nor anxiety concerning dress; it keeps holiday from earthly cares, and devotes all its energies to the acquisition of the good things which are eternal, and asks only how may be made to flourish in it self-control and manly courage, righteousness and wisdom, and all the other virtues, which, distributed under these heads, properly enable the good man to discharge all the duties of life.]
Source: Letters (New Advent)