Dr. C.F.W. Walther quoting Luther's comments on Genesis 27:38:
“When we were still monks, we accomplished nothing by our mortifications of the flesh, for we refused to admit our sin and our godless way of life. As a matter of fact, we knew nothing about original sin, and we didn’t understand that unbelief is sin. And, what is more, we also believed and taught that one must doubt God’s grace and mercy. That is why, the harder I ran and desired to come to Christ, the further He receded from me. After confession and when I had conducted Mass, my heart was never at peace, for conscience can never find real, abiding comfort in good works.” (II, 467, [cf. LW 5, 157])
Our works cannot justify us, or give us true comfort. Only faith in Jesus Christ justifies.
C.F.W. Walther, Essays for the Church, Vol. 1 (St. Louis: CPH, 1992) 268.