By faith we are reborn into the family of God. Absolutely, agrees James. But God wants more than justified infants; He wants mature daughters and sons. Faith is foundational, but it must be genuine, proven faith, evident to the world. James' exhortation is a challenge to Christians of every age to keep growing up.
Christians have a lifelong goal: to become like Christ. This involves change, and change isn't always easy. But the more you know of God's purposes for you, the more you can experience His joy and participate in His plan.