Tim Keller has a great article called Advancing the Gospel into the 21st Century. The following paragraphs are particularly insightful:
The gospel produces a unique blend of humility and boldness/joy in the convert. If you preach just a demanding God, the listener will have "low self-esteem"; if you preach just an all-loving God, the listener will have higher self-esteem. But the gospel produces something beyond both of those. The gospel says: I am so lost Jesus had to die to save me. But I am so loved that Jesus was glad to die to save me. That changes the very basis of my identity- -it transforms me from the root.
I can't tell you how important this is in all mission and ministry. Unless you distinguish the gospel from both religion and irreligion–from both traditional moralism and liberal relativism–then newcomers in your services will automatically think you are simply calling them to be good and nice people. They will be bored. But when, as here in Acts 15, the gospel is communicated in its unique, counter-intuitive balance of truth and love, then listeners will be surprised. Most people today try to place the church somewhere along a spectrum from "liberal" to "conservative"–from the relativistic to the moralistic. But when they see a church filled with people who insist on the truth, but without a shred of superiority or self-righteousness–this simply explodes their categories. To them, people who have the truth are not gracious, people who are gracious and accepting say "who knows what is the truth?" Christians are enormously bold to tell the truth, but without a shred of superiority, because you are sinner saved by grace. This balance of boldness and utter humility, truth and love–is not somewhere in the middle between legalistic fundamentalism and relativistic liberalism. It is actually off the charts.
Paul knew that 'getting the gospel straight'–not falling off into either legalism on the one hand or license on the other–is absolutely critical to the mission of the church. The secret of ministry power is getting the gospel clear. To be even slightly off to one side or another, loses tons of spiritual power. And people don't get really converted. Legalistic churches reform people's behavior through social coercion, but the people stay radically insecure and hyper-critical. They don't achieve the new inner peace that the grace of God brings. The more relativistic churches give members some self-esteem and the veneer of peace but in the end that is superficial too. The result, Archibald Alexander said, is like trying to put a signet ring on the wax to seal a letter, but without any heat! Either the ring will affect the surface of the wax only or break it into pieces. You need heat to permanently change the wax into the likeness of the ring. So without the Holy Spirit working through the gospel, radically humbling and radically exalting us and changing them from the inside out, the religion either of the hard or soft variety will not avail.