In Psalms of lament, we find cries of desperation that yearn for deliverance from a broken, fallen world.  This Psalm is unique in that David's oppressor is not a physical foe, as it often is elsewhere, but something far more serious.  He is confronted with his sin and God's judgment, the great problem that has plagued mankind since our Fall.  Both his conscience and Nathan's message spoke a word of law, opening his eyes to the depth of his sin (Guilt); he was sinful in his actions and in his very nature.  But he did not respond by trying to "make up for it" but by seeking God's Grace in forgiveness (justification) and also in inward renewal (sanctification).  Though engulfed by the law's message of darkness and gloom, he searched for a comforting word: "Let me hear joy and gladness!"  He then vowed that, if God came to his rescue, he would show his Gratitude by teaching sinners about His mercy.  Did God forgive this man, who had committed adultery and murder?  Nathan responded to him with these words: "The Lord has put away your sin."  Christ's sacrifice is enough for even the greatest of sinners.