Grace-driven effort is violent. It is aggressive. The person who understands the gospel understands that, as a new creation, his spiritual nature is in opposition to sin now, and he seeks not just to weaken sin in his life but to outright destroy it. Out of love for Jesus, he wants sin starved to death, and he will hunt and pursue the death of every sin in his heart until he has achieved success.
This is a very different pursuit than simply wanting to be good. It is the result of having transferred one’s affections to Jesus. When God’s love takes hold of us, it powerfully pushes out our own love for other gods and frees our love to flow back to him in true worship. And when we love God, we obey him. The moralist doesn’t operate that way. While true obedience is a result of love, moralistic legalism assumes it works the other way around, that love results from obedience.