You may have heard it taught, as I have, that sanctification is a life of daily repentance. I believe this is true because this conclusion acknowledges the fact that we are not perfect and will likely sin sometimes (rarely, we hope). So, if we Christians do sin, then repentance is required again, not in order to reapply for justification, but in order for us to continue in the process of sanctification.
In fact, if this were not so, sanctification would not be necessary at all, for we would have achieved perfection. How can we ever hope to grow in holiness except to repent of particular sins for which we have not yet offered repentence and to repent of that to which we have returned whether by premeditation or impulse?
This daily repentance can encourage us to persevere against any sinful habits we have. Not only so, but we should not feel defeated or discouraged from a genuine pursuit of sanctification by occasional (or perhaps even habitual) 'back-sliding'.
"What a wretched man I am! Who will rescue me from this body of death? Thanks be to God -- through Jesus Christ our Lord!" ~Romans 7:24-25
"Because he himself suffered when he was tempted, he is able to help those who are being tempted." ~Hebrews 2:18
"Father, I want those you have given me to be with me where I am, and to see my glory, the glory you have given me because you loved me before the creation of the world." ~John 17:24