In his wonderful book, You Can Change: God’s Transforming Power for Our Sinful Behavior and Negative Emotions, Tim Chester beautifully illustrates the difference between fighting sin with rules and legalism and fighting sin with the beauty of the gospel:
In Greek mythology, the Sirens would sing enchanting songs, drawing sailors irresistibly toward the rocks and certain shipwreck. Odysseus filled his crew’s ears with wax and had them tie him to the mast. This is like the approach of legalism. We bind ourselves up with laws and disciplines in a vain attempt to resist temptation. Orpheus, on the other hand, played such beautiful music on his harp that his sailors ignored the seductions of the Sirens’ song. This is the way of faith. The grace of the gospel sings a far more glorious song than the enticements of sin, if only we have the faith to hear its music.