I disagree. He's talking about them being able to do something that they were incapable of doing before they were saved - but you would have to start reading from chapter 1 to see it - particularly chapter 3. Also Rom 6:17-18 shows the final result - the guarantee so to speak: "But thanks be to God, that you who were once slaves of sin have become obedient from the heart to the standard of teaching to which you were committed, 18 and, having been set free from sin, have become slaves of righteousness."
And the wrong choice ends in death - v16
Actually - the struggle is proof of genuine faith. We all do struggle. We all still sin - but we should be striving to live a sin free life as chapter 7 also indicates.