When Christians Sin

"Let us say that I have been living in the light of what God has been giving us for the present life. As a born-again child of God, I have been practicing the reality of true spirituality, as Christ has purchased it for us.
And then sin reenters.
For some reason my moment-by-moment belief in God falters--a fondness for some specific sin has caused me at that point not to draw in faith upon the fact of a restored relationship with the Trinity. The reality of the practice of true spirituality suddenly slips from me. I look up some morning, some afternoon, some night--and something is gone, something I have known: my quietness and my peace are gone. It is not that I am lost again, because justification is once for all. But . . . there is no exhibition of the victory of Christ upon the cross. Looking at me at this point, men would see no demonstration that God's creation of moral rational creatures is not a complete failure, or even that God exists. . . .
At this point a question must arise: Is there a way back? Or is it like a fine Bavarian porcelain cup, dropped to a tile floor so that it is smashed beyond repair?
Thank God, the gospel includes this. The Bible is always realistic; it is not romantic, but deals with realism--with what I am. There is a way back, and the basis of the way back is nothing new to us. The basis is again the blood of Christ, the finished work of the Lamb of God: the once-for-all completed work of Christ upon the cross, in space, time, and history."
--Francis Schaeffer, True Spirituality (Tyndale House, 2011), 86-87; italics original

This is worth reflecting on, not only for yourself when you sin but in helping other Christians when they sin.