In saying that Christianity is the religion of the broken heart, we do not mean that Christianity ends with the broken heart; we do not mean that the characteristic Christian attitude is a continual beating on the breast or a continual crying of “Woe is me.” Nothing could be further from the fact. On the contrary, Christianity means that sin is faced once for all, and then is cast, by the grace of God, forever into the depths of the sea. The trouble with the paganism of ancient Greece, as with the paganism of modern times, was not in the superstructure, which was glorious, but in the foundation, which was rotten. There was always something to be covered up; the enthusiasm of the architect was maintained only by ignoring the disturbing fact of sin. In Christianity, on the other hand, nothing needs to be covered up. The fact of sin is faced squarely once for all, and is dealt with by the grace of God. But then, after sin has been removed by the grace of God, the Christian can proceed to develop joyously every faculty that God has given him. Such is the higher Christian humanism–a humanism founded not upon human pride but upon divine grace.
But although Christianity does not end with the broken heart, it does begin with the broken heart; it begins with the consciousness of sin. Without the consciousness of sin, the whole of the gospel will seem to be an idle tale. But how can the consciousness of sin be revived? Something no doubt can be accomplished by the proclamation of the law of God, for the law reveals transgressions. The whole of the law, moreover, should be proclaimed. It will hardly be wise to adopt the suggestion (recently offered among many suggestions as to the ways in which we shall have to modify our message in order to retain the allegiance of the returning soldiers) that we must stop treating the little sins as though they were big sins. That suggestion means apparently that we must not worry too much about the little sins, but must let them remain unmolested.
J. Gresham Machen, Christianity and Liberalism (Kindle Edition)