The Imitation of Christ, by Thomas a Kempis, tr. by William Benham , at sacred-texts.com
"My Son, I must be thy Supreme and final end, if thou desirest to be truly happy. Out of such purpose thy affection shall be purified, which too often is sinfully bent upon itself and upon created things. For if thou seekest thyself in any matter, straightway thou wilt fail within thyself and grow barren. Therefore refer everything to Me first of all, for it is I who gave thee all. So look upon each blessing as flowing from the Supreme Good, and thus all things are to be attributed to Me as their source.
2. "From Me the humble and great, the poor and the rich, draw water as from a living fountain, and those who serve Me with a free and faithful spirit shall receive grace for grace. But he who will glory apart from Me, or will be delighted with any good which lieth in himself, shall not be established in true joy, nor shall be enlarged in heart, but shall be greatly hindered and thrown into tribulation. Therefore thou must not ascribe any good to thyself, nor look upon virtue as belonging to any man, but ascribe it all unto God, without whom man hath nothing. I gave all, I will receive all again, and with great strictness require I the giving of thanks.
3. "This is the Truth, and by it the vanity of boasting is put to flight. And if heavenly grace and true charity shall enter into thee, there shall be no envy, nor straitening of the heart, nor shall any self-love take possession of thee. For divine charity conquereth all things, and enlargeth all the powers of the soul. If thou art truly wise, thou wilt rejoice in Me alone, thou wilt hope in Me alone; for there is none good but one, that is God,(1) Who is to be praised above all things, and in all things to receive blessing."
(1) Luke xviii. 19.