The Epistle to the Romans - Session 28 - Romans 6:1-2

Romans chapter 6 and 7 deal with the issue of indwelling sin. Why is it that those who have been justified continue to struggle with sin? Does not the Holy Spirit give us victory over sin? In Romans 6:1-2, Paul answers those who believe that if God is glorified in showing grace to us when we sin, they why don't we really sin, so He can be really glorified?