The more we discussed the Gospel, the more it became clear that he did not understand it. He talked about working hard to be a “good christian” and teaching others to be “good christians” by following Christ’s ethical example.
“What about Jesus as Savior?” I asked. “Of course Christ is the Savior,” he answered.
“What does it mean that Jesus is the Savior?” I implored.
“It means that we can follow his example and be good Christians,” he answered. This discussion went on for several hours in various contexts.
This was troubling for two reasons: First, it is troubling for his own salvation. He has never put his faith in Christ as his Savior. He only looks to Christ as an example to follow. I think he has good intentions, he just hasn’t yet grasped the Gospel.
Second, He is a loving father with a great relationship both with his adolescent and adult children, and he loves teaching children in Sunday School. He teaches the children that they need to “try hard” to be good Christians rather than put their faith in Christ’s suffering on the cross. It is troubling that these children are not hearing the truth of the Gospel. They are hearing that they need to follow a religion, to work hard to be “good people,” in order to be accepted and loved.
This is not the Gospel.
The Gospel says that “I am more sinful and flawed than I ever dared believe,” but then quickly follows with, “I am more accepted and loved than I ever dared hope.” – Tim Keller 
But even after we put our faith in Christ as our Savior, the Gospel does not direct us to move on and then “try hard” to be good Christians.
The Gospel, faith in Christ as the Savior who died in our place and rose again, saves us to God, and also continues to infuse us with the supernatural power, through His Spirit, necessary to be transformed, to become more and more like Christ.
We never get beyond the Gospel:
“The gospel is not the first “step” in a “stairway” of truths, rather, it is more like the “hub” in a “wheel” of truth. The gospel is not just the A-B-C’s but the A-Z of Christianity. The gospel is not just the minimum required doctrine necessary to enter the kingdom, but the way we make progress in the kingdom.” – Tim Keller 
Paul thoroughly rebukes the Galatian Christians for thinking that the Gospel is something that only saves us initially, but then we grow more like Christ, becoming “good Christians” through our own efforts:
“Are you so foolish? After beginning by means of the Spirit, are you now trying to finish by means of the flesh?” (Gal. 3:3, NIV)
It is the power of Christ at work in us, through His Spirit, that transforms us to be more and more like Jesus.
So do we work at all? Do we put in any effort. Of course. But it is because of the power of the Spirit who works in us:
“For it is God who works in you to will and to act in order to fulfill his good purpose.” – Philippians 2:13
But we never work to become “good Christians.” We work because we are already accepted and loved because of Christ’s work on the cross.
 Keller, Timothy. Center Church: Doing Balanced, Gospel-Centered Ministry in Your City (p. 48). Zondervan. Kindle Edition.
Timothy Keller, “The Centrality of the Gospel,” http://www.newcityindy.org/wp-content/uploads/2011/07/centrality-of-gospel.-keller.pdf