2 Corinthians 12:9-10
9 but he said to me, "My grace is sufficient for you, for power is made perfect in weakness." I will rather boast most gladly of my weaknesses, in order that the power of Christ may dwell with me.
10 Therefore, I am content with weaknesses, insults, hardships, persecutions, and constraints, for the sake of Christ; for when I am weak, then I am strong.
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From The Imitation of Christ (Thomas A. Kempis, 13th Century):
"How extremely necessary to me, O Lord, Your grace is to begin any good deed, to carry it on and bring it to completion! For without grace I can do nothing, but with its strength I can do all things in You. O Grace truly heavenly, without which our merits are nothing and no gifts of nature are to be esteemed!
Before You, O Lord, no arts or riches, no beauty or strength, no wit or intelligence avail without grace. For the gifts of nature are common to good and bad alike, but the peculiar gift of Your elect is grace or love, and those who are signed with it are held worthy of everlasting life. So excellent is this grace that without it no gift of prophecy or of miracles, no meditation be it ever so exalted, can be considered anything. Not even faith or hope or other virtues are acceptable to You without charity and grace.
O most blessed grace, which makes the poor in spirit rich in virtues, which renders him who is rich in many good things humble of heart, come, descend upon me, fill me quickly with your consolation lest my soul faint with weariness and dryness of mind. "
Link: The Imitation of Christ. Scroll down to Chapter 55: http://www.leaderu.com/cyber/books/imitation/imb3c51-59.html#RTFToC293
