A Full Savior for a Full Sinner

We like to think of ourselves with some goodness and value in ourselves and our works that God must be impressed by. Yet, the Bible describes us as sinners. Full sinners! So it is pride in our hearts that thinks we must add to Jesus' righteousness to justify us before God.
Christ is a full Savior with righteousness and works which cannot be added to by our filthy righteousness. From a sermon on Jesus' words on the cross, "It is finished," John Flavel eloquently describes how Jesus is a full Savior for a full sinner like you and me:

"Did Christ finish his work with his own hand? How dangerous and dishonourable a thing it is to join any thing of our own to the righteousness of Christ, in point of justification before God. Jesus Christ will never endure this; it reflects upon his work dishonourably; he doth not (in this case) affect social glory; not I, and my God; I, and my Christ, did this; he will be all, or none, in your justification. If he have finished the work, what need of our additions? And if not, to what purpose are they? Can we finish that which Christ could not? But we would fain be sharing with him in his honour, which he will never endure. Did he finish the work by himself, and will he ever divide the glory and praise of it with us? No, no, Christ is no half Saviour. O it is a hard thing to bring these proud hearts to live upon Christ for righteousness: we would fain add our penny to make up Christ's sum. But if you would have it so, or have nothing to do with Christ, and your penny must perish together. God gives us the righteousness of Christ as he gave manna to the Israelites in the wilderness. It is said (Deuteronomy 8:16) that "he fed with manna in the wilderness that he might humble them." The quality of the food was not humbling, for it was angels food, but the manner of giving it was so: they must live by faith upon God for it, from day to day. This was not like other food, produced by their own labour. Certainly God takes the right way humble proud nature, in calling sinners wholly from their righteousness to Christ's for their justification."