Martin Luther said: "Grace releases sin, and peace makes the conscience quiet. The two fiends that torment us are sin and conscience. But Christ has vanquished these two monsters, and trodden them under foot, both in this world, and in the world to come."
(Source: Barton, B. B. (1994). Galatians. Life application Bible commentary (8). Wheaton, Ill.: Tyndale House.)