The Imitation of Christ, by Thomas a Kempis, tr. by William Benham , at sacred-texts.com
First keep thyself in peace, and then shalt thou be able to be a peacemaker towards others. A peaceable man doth more good than a well-learned. A passionate man turneth even good into evil and easily believeth evil; a good, peaceable man converteth all things into good. He who dwelleth in peace is suspicious of none, but he who is discontented and restless is tossed with many suspicions, and is neither quiet himself nor suffereth others to be quiet. He often saith what he ought not to say, and omitteth what it were more expedient for him to do. He considereth to what duties others are bound, and neglecteth those to which he is bound himself. Therefore be zealous first over thyself, and then mayest thou righteously be zealous concerning thy neighbour.
2. Thou knowest well how to excuse and to colour thine own deeds, but thou wilt not accept the excuses of others. It would be more just to accuse thyself and excuse thy brother. If thou wilt that others bear with thee, bear thou with others. Behold how far thou art as yet from the true charity and humility which knows not how to be angry or indignant against any save self alone. It is no great thing to mingle with the good and the meek, for this is naturally pleasing to all, and every one of us willingly enjoyeth peace and liketh best those who think with us: but to be able to live peaceably with the hard and perverse, or with the disorderly, or those who oppose us, this is a great grace and a thing much to be commended and most worthy of a man.
3. There are who keep themselves in peace and keep peace also with others, and there are who neither have peace nor suffer others to have peace; they are troublesome to others, but always more troublesome to themselves. And there are who hold themselves in peace, and study to bring others unto peace; nevertheless, all our peace in this sad life lieth in humble suffering rather than in not feeling adversities. He who best knoweth how to suffer shall possess the most peace; that man is conqueror of himself and lord of the world, the friend of Christ, and the inheritor of heaven.