In the domain of Adam (Law) we lived under the rule of sin and resisted the constraint of righteousness (Romans 6:20-21). In the domain of Christ (Grace) we live under the rule of righteousness and resist the encroachment of sin (Romans 6:22-23). Before (in Adam) we didn’t resist sin because it was our natural habitat. Now (in Christ) we do resist sin because we live within a righteous standing before God. We have been transferred from one domain to the other. The struggle with sin – non-existent in our lost state – is now a normative experience in the Christian life. Ultimately, the battle against sin is a new experience for the regenerate person. Prior to our new birth there was no such experience. Point being, sin’s pressure and assault is a normal experience for believers and not an abnormal one. Anders Nygren in his commentary on Romans aptly described this reality.
“The Christians live their life on the border between two aeons. They live in Christ; but have not thereby ceased to share the fate of the children of Adam. They live in the spirit but still experience the drag of the flesh. He reminds them of the condition of their old life, and calls upon them to learn how matters stand in their new life. He speaks to them as if they were more at home in the world of sin than in the world of grace and righteousness.” – Anders Nygren, p. 259.