27 You must also be careful to avoid the snare of a passion for vainglory. “How,” Jesus says, “can you believe which receive glory one from another?” What an evil that must be the victim of which cannot believe! Let us rather say: “You are my glorying,” and “He that glories, let him glory in the Lord,” and “If I yet pleased men I should not be the servant of Christ,” and “Far be it from me to glory save in the cross of our Lord Jesus Christ, through whom the world has been crucified unto me and I unto the world;” and once more: “In God we boast all the day long; my soul shall make her boast in the Lord.” When you do alms, let God alone see you.
When you fast, be of a cheerful countenance. Let your dress be neither too neat nor too slovenly; neither let it be so remarkable as to draw the attention of passers-by, and to make men point their fingers at you. Is a brother dead? Has the body of a sister to be carried to its burial? Take care lest in too often performing such offices you die yourself. Do not wish to seem very devout nor more humble than need be, lest you seek glory by shunning it. For many, who screen from all men's sight their poverty, charity, and fasting, desire to excite admiration by their very disdain of it, and strangely seek for praise while they profess to keep out of its way.
From the other disturbing influences which make men rejoice, despond, hope, and fear I find many free; but this is a defect which few are without, and he is best whose character, like a fair skin, is disfigured by the fewest blemishes. I do not think it necessary to warn you against boasting of your riches, or against priding yourself on your birth, or against setting yourself up as superior to others. I know your humility; I know that you can say with sincerity: “Lord, my heart is not haughty nor my eyes lofty;” I know that in your breast as in that of your mother the pride through which the devil fell has no place.
It would be time wasted to write to you about it; for there is no greater folly than to teach a pupil what he knows already. But now that you have despised the boastfulness of the world, do not let the fact inspire you with new boastfulness. Harbor not the secret thought that having ceased to court attention in garments of gold you may begin to do so in mean attire. And when you come into a room full of brothers and sisters, do not sit in too low a place or plead that you are unworthy of a footstool.
Do not deliberately lower your voice as though worn out with fasting; nor, leaning on the shoulder of another, mimic the tottering gait of one who is faint. Some women, it is true, disfigure their faces, that they may appear unto men to fast. As soon as they catch sight of any one they groan, they look down; they cover up their faces, all but one eye, which they keep free to see with. Their dress is sombre, their girdles are of sackcloth, their hands and feet are dirty; only their stomachs— which cannot be seen— are hot with food.
Of these the psalm is sung daily: “The Lord will scatter the bones of them that please themselves.” Others change their garb and assume the mien of men, being ashamed of being what they were born to be— women. They cut off their hair and are not ashamed to look like eunuchs. Some clothe themselves in goat's hair, and, putting on hoods, think to become children again by making themselves look like so many owls.
Source: Letters (New Advent)