When Christians come to understand how we are created as tripartite creatures, with a body, soul (mind, will and emotions) and spirit, we will understand God's word a bit better concerning this matter of sin. When we are born again, our spirits become born again, pure and unable to sin, for that is where God dwells in us. It is the soul and body that continues to become sanctified and the battle against sin is waged---through its connection to the soul and then the body, transferring God's goodness and wisdom and righteousness in hopefully steady increments, until we finally go to be with Jesus in death.