6 But we too were there. He goes to the members. “I have called to mind the days of old”. Did He “call to mind the days of old,” by whom every day was made? No, but the body speaks, each one who has been justified by His grace, who dwells in Him in love and devout humility, speaks and says, “I have meditated upon all Your works:” plainly because You have made all things good, and nothing would have stood fast, which was not established by You. Your creation is made a spectacle unto me: I have sought in the work the Artificer, in all that is made the Maker.
Wherefore this, to what purpose this, save that he might understand, that whatever there was of good in himself was made by Him....Look back then upon the Framer of your life, the Author of your substance, of your righteousness, and of your salvation: “meditate upon the works of His hands,” for the righteousness too which is in you, you will find to pertain to His hand. Hear the Apostle teaching you this, “not of works,” he says, “lest any should boast.” Have we no good works?
Plainly we have: but see what follows; “for we are His workmanship,” says he. “We are His workmanship:” perhaps in thus speaking of workmanship, he meant to mention the nature whereby we are men? Evidently not: he was speaking of works. But let us not make conjectures; let the text go on, “for we are His workmanship, created in Christ Jesus unto good works.” Think not then that you yourself doest anything, save in so far as you are evil....“Work out your own salvation,” says the Apostle, “with fear and trembling.” If we do work out our own salvation, wherefore with fear, wherefore with trembling, when what we work is in our own power?
Hear wherefore with fear and trembling: “for it is God that works in you both to will and to do, of His good pleasure.” Therefore “with fear and trembling,” that it may delight our Maker to work in the lowly valley....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)