God has assuredly promised his grace to the humble, that is, to those who lament and despair of themselves.
But no man can be thoroughly humbled until he knows that his salvation is utterly beyond his own powers, devices, endeavors, will, and works, and depends entirely on the choice, will, and work of another, namely, of God alone.
For as long as he is persuaded that he himself can do even the least thing toward his salvation, he retains some self-confidence and does not altogether despair of himself, and therefore he is not humbled before God, but presumes that there is--or at least hopes or desires that there may be--some place, time, and work for him, by which he may at length attain to salvation. But when a man has no doubt that everything depends on the will of God, then he completely despairs of himself and chooses nothing for himself, but waits for God to work; then he has come close to grace.
-- Martin Luther, Bondage of the Will, in LW, 33:61-62