The Imitation of Christ, by Thomas a Kempis, tr. by William Benham , at sacred-texts.com
"My Son, I have said, Peace I leave with you, My peace I give unto you, not as the world giveth give I unto you.(1) All men desire peace, but all do not care for the things which belong unto true peace. My peace is with the humble and lowly in heart. Thy peace shall be in much patience. If thou heardest Me, and didst follow My voice, thou shouldest enjoy much peace."
2. What then shall I do, Lord?
3. "In everything take heed to thyself what thou doest, and what thou sayest; and direct all thy purpose to this, that thou please Me alone, and desire or seek nothing apart from Me. But, moreover, judge nothing rashly concerning the words or deeds of others, nor meddle with matters which are not committed to thee; and it may be that thou shalt be disturbed little or rarely. Yet never to feel any disquiet, nor to suffer any pain of heart or body, this belongeth not to the present life, but is the state of eternal rest. Therefore count not thyself to have found true peace, if thou hast felt no grief; nor that then all is well if thou hast no adversary; nor that this is perfect if all things fall out according to thy desire. Nor then reckon thyself to be anything great, or think that thou art specially beloved, if thou art in a state of great fervour and sweetness of spirit; for not by these things is the true lover of virtue known, nor in them doth the profit and perfection of man consist."
4. In what then, Lord?
5. "In offering thyself with all thy heart to the Divine Will, in not seeking the things which are thine own, whether great or small, whether temporal or eternal; so that thou remain with the same steady countenance in giving of thanks between prosperity and adversity, weighing all things in an equal balance. If thou be so brave and long-suffering in hope that when inward comfort is taken from thee, thou even prepare thy heart for the more endurance, and justify not thyself, as though thou oughtest not to suffer these heavy things, but dost justify Me in all things that I appoint, and dost bless My Holy Name, then dost thou walk in the true and right way of peace, and shalt have a sure hope that thou shalt again behold My face with joy. For if thou come to an utter contempt of thyself, know that then thou shalt enjoy abundance of peace, as much as is possible where thou art but a wayfaring man."
(1) John xiv. 27.