A Voice from the Past - Martin Luther

When the Law accuses and sin terrifies you, and you do not feel anything except the wrath and judgment of God, do not despair on that account. But "take the armor of God, the shield of faith, the helmet of hope, and the sword of the Spirit" (Eph. 6:13, 16, 17); and find out by experience what a good and brave warrior you are. By faith take hold of Christ, the Lord of the Law and of sin and of everything that accompanies them. When you believe in Him, you are justified -- something that your reason and the consciousness of your heart do not tell you amid your temptation, but only the Word of God.

Martin Luther, 1483-1546, Commentary on Galatians 1535, 5:5 (Luther's Works, Vol. 27, edited and translated by Jaroslav Pelikan, 1964, Concordia Press, p.26)

What does this say about dealing with doubt?