Read Salvation if Found in Christ Alone, by Alistair Begg, at Truth for Life.
"What an extraordinary reality we as Christians have in this assurance from the Apostle Paul! Despite our best efforts, every day we come face-to-face with our sinful nature. Nonetheless, we can find peace in the certainty that our sin has been dealt with once and for all on the cross."
Therefore there is now no condemnation for those who are in Christ Jesus. For the law of the Spirit of life in Christ Jesus has set you free from the law of sin and of death. For what the Law could not do, weak as it was through the flesh, God did: sending His own Son in the likeness of sinful flesh and as an offering for sin, He condemned sin in the flesh, so that the requirement of the Law might be fulfilled in us, who do not walk according to the flesh but according to the Spirit.