Repentance doesn't necessarily mean that you're going to stop sinning.
Part of repentance is recognizing that the sins I do occur because of the sinner I am. And the sinful nature is going to keep on being sinful until I'm laid to rest in the grave.
Here's what repentance really is: that I'm not going to rely on myself and my own efforts to solve the problem of sin in my life. Rather, repentance means that I flee again to Christ, and depend all the more upon His forgiveness.
So does this mean the Christian can sin-like-crazy and indulge in whatever the Old Adam might desire? [She sighs in exasperation and wonders, "Are you for-real??"]
The reason the Christian desires to amend his sinful life is precisely because there has been a change of heart, worked by the Gospel, which causes him to be distressed by sin and to yearn to be free of it.
The Confessions state that the "Holy Spirit works faith when and where He pleases in those who hear the Gospel." It is also true He works the fruits of faith when and where He pleases. The Lord may have different ideas about what is good in our life than we do. When we make an idol of our "good Christian walk," then the Lord knows better than we what is good for us.
We tend to think of the "amendment of life" as doing this, stopping that, fixing that habit. Even bigger, though, is letting go of the sins of others, where Christ's forgiveness flows through us to others who've been rotten and don't deserve kindness. Hmm ... just like Jesus forgives us.