Sanctification is not a repair job. God is after something new.
But is there not such a thing as growth in sanctification?, progress in the Christian life? ... There is a kind of growth and progress, but it is growth in "grace", a growth in coming to be captivated more and more by the totality and the unconditionality of the grace of God. It is a matter of getting used to the fact that if we are to be saved, it will have to be by grace alone.
We should make no mistake about it: sin is to be conquered and expelled. But if we see that sin is the total state of standing against the unconditional grace and goodness of God, if sin is our very incredulity, unbelief, mistrust, and insistence on falling back on our self to maintain control, then it is only through the total grace of God that sin comes under attack, and only through faith in that total grace that sin is defeated. To repeat: sin is not defeated by a repair job, but by dying and being raised new.
(from his essay, "A Lutheran View of Sanctification")