The Imitation of Christ, by Thomas a Kempis, tr. by William Benham , at sacred-texts.com
The testimony of a good conscience is the glory of a good man. Have a good conscience and thou shalt ever have joy. A good conscience is able to bear exceeding much, and is exceeding joyful in the midst of adversities; an evil conscience is ever fearful and unquiet. Thou shalt rest sweetly if thy heart condemn thee not. Never rejoice unless when thou hast done well. The wicked have never true joy, nor feel internal peace, for there is no peace, saith my God, to the wicked.(1) And if they say "we are in peace, there shall no harm happen unto us, and who shall dare to do us hurt?" believe them not, for suddenly shall the wrath of God rise up against them, and their deeds shall be brought to nought, and their thoughts shall perish.
2. To glory in tribulation is not grievous to him who loveth; for such glorying is glorying in the Cross of Christ. Brief is the glory which is given and received of men. Sadness always goeth hand in hand with the glory of the world. The glory of the good is in their conscience, and not in the report of men. The joy of the upright is from God and in God, and their joy is in the truth. He who desireth true and eternal glory careth not for that which is temporal; and he who seeketh temporal glory, or who despiseth it from his heart, is proved to bear little love for that which is heavenly. He who careth for neither praises nor reproaches hath great tranquillity of heart.
3. He will easily be contented and filled with peace, whose conscience is pure. Thou art none the holier if thou art praised, nor the viler if thou art reproached. Thou art what thou art; and thou canst not be better than God pronounceth thee to be. If thou considerest well what thou art inwardly, thou wilt not care what men will say to thee. Man looketh on the outward appearance, but the Lord looketh on the heart:(2) man looketh on the deed, but God considereth the intent. It is the token of a humble spirit always to do well, and to set little by oneself. Not to look for consolation from any created thing is a sign of great purity and inward faithfulness.
4. He that seeketh no outward witness on his own behalf, showeth plainly that he hath committed himself wholly to God. For not he that commendeth himself is approved, as St. Paul saith, but whom the Lord commendeth.(3) To walk inwardly with God, and not to be held by any outer affections, is the state of a spiritual man.
(1) Isaiah lvii. 21. (2) 1 Samuel xvi. 7. (3) 2 Corinthians x. 18.