Now may the God of peace himself sanctify you completely, and may your whole spirit and soul and body be kept blameless at the coming of our Lord Jesus Christ.—1 Thessalonians 5:23
Not a single one of us is a perfect repenter. And not a single one of us ever will be. I do believe we cooperate in the work of our sanctification, working out what God has worked in (Phil. 2:12-13), striving to lay hold of the holiness with which God has already laid hold of us (Phil. 3:12), holding true to what we've already attained (Phil. 3:16), but the power and the success of sanctification must be the Lord's alone, if only because only he sees all we need cleansing from.
It is a mistake to think that as we progress in sanctification we have less sin to address. We walk through victories, successions of freedoms, but my experience has been that the further into Christ's righteousness I press, the more of my own unworthiness I see, not the less. And even as the Spirit bears more and more fruit in my life, even as I learn to trust more and more, when I do finally cross that heavenly finish line, there will nevertheless still be sins unrepented, especially among the sins I don't even remember or don't even see. And I will pull my sorry self across that line, some stupid sin still entangled around my ankle, and I will look up to see Christ the Judge standing over me, looking down, considering my pitiful soul. And do you know what he will say? "Well done."
Now to him who is able to keep you from stumbling and to present you blameless before the presence of his glory with great joy, to the only God, our Savior, through Jesus Christ our Lord, be glory, majesty, dominion, and authority, before all time and now and forever. Amen.—Jude 1:24-25