
Tim Keller from his book The Prodigal God on the need to repent, not simply of our unrighteousness, but our righteousness also:
We must learn how to repent of the sin under all our other sins and under all our righteousness – the sin of seeking to be our own Savior and Lord. We must admit that we’ve put our ultimate hope in both our wrongdoing and right doing we have been seeking to get around God or get control of God in order to get hold of those things. It is only when you see the desire to be your own Savior and Lord—lying beneath both your sins and your moral goodness—that you are on the verge of becoming a Christian indeed. When you realize that the antidote to being bad is not just being good, you are on the brink. If you follow through, it will change everything—how you relate to God, self, others, the world, your work, you sins, your virtue. It’s called the new birth because its so radical”
- shared from Tullian Tchividjian at the Gospel Coalition: Repenting of Our Good Works

So although 2 Corinthians 5:17 and Ezekiel 36:26 speak of a decisive change that always occurs in the heart of every new believer, the outworking of that change is not instantaneous and absolute. Instead it is progressive over time and never complete in this life. However, the awareness of this internal struggle with sin should never be used as an excuse for sinful behavior. Rather, we should always keep in mind that we are saints called to live a life that is set apart for God.
6 And the Lord your God will circumcise your heart and the heart of your offspring, so that you will love the Lord your God with all your heart and with all your soul, that you may live.
“Sanctify them through Thy truth.” –John 17:17
32 Two others, who were criminals, were led away to be put to death with him. 33 And when they came to the place that is called The Skull, there they crucified him, and the criminals, one on his right and one on his left. 34 And Jesus said, 