As long as a person thinks he is right he is going to be incomprehensibly proud and presumptuous. He is going to hate God, despise His grace and mercy, and ignore the promises in Christ. The Gospel of the free forgiveness of sins through Christ will never appeal to the self-righteous.
This monster of self-righteousness, this stiff-necked beast, needs a big axe. And that is what the Law is, a big axe. Accordingly, the proper use and function of the Law is to threaten until the conscience is scared stiff.—Martin Luther, Homily for Trinity XIII (Epistle), Church Postils.