...If you are a preacher of mercy, do not preach an imaginary but the true mercy. If the mercy is true, you must therefore bear the true, not an imaginary sin. God does not save those who are only imaginary sinners. Be a sinner, and let your sins be strong, but let your trust in Christ be stronger, and rejoice in Christ who is the victor over sin, death, and the world.
We will commit sins while weare here, for this life is not a place where justice resides. We, however, says Peter (2. Peter 3:13) are looking forward to a new heaven and a new earth where justice will reign. It suffices that through God's glory we have recognized the Lamb who takes away the sin of the world. No sin can separate us from Him, even if we were to kill or commit adultery thousands of times each day*. Do you think such an exalted Lamb paid merely a small price with a meager sacrifice for our sins?
Pray hard, for you are quite a sinner.
--From a letter to fellow scrupe sufferer Phillip Melanththon, 1521
*A believer, as Luther always insisted, will not willingly commit sin. His point here is not that we should or even dare give our fallen nature its head- no believer would ever consider such a thing- but rather that no sin can harm a person who by faith is joined to the One Who has conquered sin on our behalf.