Sanctification is a beautiful grace from God in which, He transforms us more and more into the image of Christ. It should never be used as the sole measure of our justification and assurance. When a believer is united to Christ by faith alone, Christ is to them “wisdom from God, righteousness and sanctification and redemption” 1st Corinthians 1:30. “Moreover, although we do good works we do not base our salvation on them; for we cannot do any work that is not defiled by our flesh and also worthy of punishment. And even if we could point to one, memory of a single sin is enough for God to reject that work. So we would always be in doubt, tossed back and forth without any certainty, and our poor consciences would be tormented constantly if they did not rest on the merit of the suffering and death of our Savior” Belgic confession - Article 24