Legalism says God will love us if we change. The gospel says God will change us because He loves us.

The apostle Paul claimed the Law is written on the 'fleshy tables' of the human heart (2 Cor. 3:3 KJV). What he meant are these 'shoulds' and 'shouldn'ts' are both instinctual and inescapable, part of our DNA. They are a psychological reality. We may justify our actions away, but deep down, we know when we've done something wrong.

The way of God's grace becomes indispensable when we realize that the way of God's law is inflexible.

The gospel is not about a lifestyle that we live, it's about the law-fulfilling life that Christ lived.