In "Biblical Perspective" Gordon Snider writes concerning Romans 5:10:
Paul presented additional reasons why the justified can have confidence. When we were enemies probably means not only that man was in rebellion against God, but that God also considered us to be deserving of punishment. We were reconciled . . . by the death of his Son. Reconciliation is a new term in Paul's argument. The cross did not change the fact that natural man is still a rebel against God, but it did make it possible for God to reach out to the sinner. Since the death of Christ has removed our alienation from God, we can have even greater confidence that we shall be saved by his life. The death of Christ changed our spiritual position. The life of Christ changes our daily performance and guarantees our future glorification.
Source: Studies in Romans: Adult Teacher's Insights, page 17.