When the will is enchained as the slave of sin, it cannot make a movement toward goodness, far less steadily pursue it. Every such movement is the first step in the conversion to God, which in Scripture is entirely ascribed to divine grace. 

Nevertheless, there remains a will which both inclines and hastens on with the strongest affection toward sin; man, when placed under this bondage, being deprived not of will, but of soundness of will. Bernard says not improperly, that all of us have a will; but to will well is proficiency, to will ill is defect. Thus simply to will is the part of man, to will ill the part of corrupt nature, to will well the part of grace.

Man, since he was corrupted by the fall, sins not forced or unwilling, but voluntarily, by a most forward bias of the mind; not by violent compulsion, or external force, but by the movement of his own passion; and yet such is the depravity of his nature, that he cannot move and act except in the direction of evil.

“Thus the soul, in some strange and evil way, is held under this kind of voluntary, yet sadly free necessity, both bond and free; bond in respect of necessity, free in respect of will: and what is still more strange, and still more miserable, it is guilty because free, and enslaved because guilty, and therefore enslaved because free.” Bernard of Clairvaux, In Cantica

God, therefore, begins the good work in us by exciting in our hearts a desire, a love, and a study of righteousness, or (to speak more correctly) by turning, training, and guiding our hearts unto righteousness and he completes this good work by confirming us unto preseverance. But lest any one should cavil that the good work thus begun by the Lord consists in aiding the will, which is in itself weak, the Spirit elsewhere declares what the will, when left to itself, is able to do. His words are, “A new heart also will I give you , and a new spirit will I put within you; and I will take away the stony heart out of your flesh, and I will give you an heart of flesh. And I will put my Spirit within you, and cause you to walk in my statutes, and ye shall keep my judgements, and do them” (Ezek. 36:26, 27) How can it be said that the weakness of the human will is aided so as to enable it to aspire effectually to the choice of good, when the fact is, that, it must be wholly transformed and renovated?

Hence the psalmist, after saying that the Lord “has made us,” to deprive us of all shard in the work, immediately adds, “not we ourselves.” That he is speaking of regeneration, which is the commencement of the spiritual life, is obvious from the context, in which the next words are, “we are his people, and the sheep of his pasture.” (Ps. 100:3) Not contented with simply giving God the praise of our salvation, he distinctly excludes us from all share in it, just as if he had said that not one particle remains to man as a ground of boasting. The whole is of God.