The Imitation of Christ, by Thomas a Kempis, tr. by William Benham , at sacred-texts.com
Vain is the life of that man who putteth his trust in men or in any created Thing. Be not ashamed to be the servant of others for the love of Jesus Christ, and to be reckoned poor in this life. Rest not upon thyself, but build thy hope in God. Do what lieth in thy power, and God will help thy good intent. Trust not in thy learning, nor in the cleverness of any that lives, but rather trust in the favour of God, who resisteth the proud and giveth grace to the humble.
2. Boast not thyself in thy riches if thou hast them, nor in thy friends if they be powerful, but in God, who giveth all things, and in addition to all things desireth to give even Himself. Be not lifted up because of thy strength or beauty of body, for with only a slight sickness it will fail and wither away. Be not vain of thy skilfulness or ability, lest thou displease God, from whom cometh every good gift which we have.
3. Count not thyself better than others, lest perchance thou appear worse in the sight of God, who knoweth what is in man. Be not proud of thy good works, for God's judgments are of another sort than the judgments of man, and what pleaseth man is ofttimes displeasing to Him. If thou hast any good, believe that others have more, and so thou mayest preserve thy humility. It is no harm to thee if thou place thyself below all others; but it is great harm if thou place thyself above even one. Peace is ever with the humble man, but in the heart of the proud there is envy and continual wrath.