Do not preach as if there are two ways: living God's way or living man's way.
Because there are three ways to live: moralistically, irreligiously, and the gospel.
'Round these here parts, we preach against the first two. Gospel wakefulness is rare where Christianity is cultural; cultural Christians believe Christianity is about being a better Christian. (Some of the hippest, slickest, most casual, and easy going churches around here are the most legalistic, and they don't even know it because they think legalism is about suits and ties and not drinking.) And so gospel-centered preaching calls for repentance from moralism and religion as often as it does from immorality.
Here's Tim Keller explaining the three ways: