Nobody will ever come before God and say, "I did it by the strength of my own hands." Though this person may have faith and a strong will, he is certainly not perfect. Many times, when the Israelites' faith broke down, God had to intervene in some way to save them. Whether it is Israel at the Red Sea or Israel out in the wilderness, time and again He had to intervene and spare them, even in times when they showed a measure of faith.
Since man's creation, humans have been exalting themselves against God by choosing to do things their own way. However, there is only one way that works eternally, and every human being will be led to see his weaknesses and know that it is by grace that we are saved. This realization does wonders to a person's feelings about himself, making humility possible. This, in turn, makes it possible for him to yield to God, which makes it possible for him to deal with other human beings, not with a high hand or as a master to a slave, but as a friend—as an understanding brother or sister who has gone through similar experiences and seen their own failures, and who can commiserate, sympathize, show compassion and mercy, encourage, and inspire the one who has failed.
God will work in each person and will do it in such a way that he will come to realize that merely knowing the truth—and even believing the truth and acting on it—are not enough. God must save them by grace.
This is not to say that works are unimportant. They are vital to maintaining and developing a relationship with God. They are important in building character, and in this sense, without works we will have a difficult time being saved. If nothing else, doing good works shows that a relationship exists between a person and God. So works are important to earning rewards, to building character, to providing a witness for God, but they still will not save us of and by themselves because, since we are imperfect, they are also terribly flawed.