Through the person and work of Jesus Christ, God fully accomplishes salvation for us, rescuing us from judgment for sin into fellowship with him, and then restores the creation in which we can enjoy our new life together with him forever.
Without the gospel we hate ourselves instead of our sin. Without the gospel we’re motivated through all sorts of awful fear and pride to change and it doesn’t really change our hearts; it just restrains our hearts.
Faith in the gospel restructures our motivations, our self-understanding, our identity, and our view of the world. Behavioral compliance to rules without heart-change will be superficial and fleeting… We can only change permanently as we take the gospel more deeply into our understanding and into our hearts. We must feed on the gospel, as it were, digesting it and making it part of ourselves. That is how we grow.