"Professional Christians" are people who say the right things and do the right things. By all outward appearances, they are followers of Christ. But inside, they're tired, apathetic, and maybe even angry toward God for making them follow a bunch of rules. According to J.D. Greear in Gospel: Recovering the Power that Made Christianity Revolutionary (B&H Publishing Group, 2011), their problem is that they have substituted godly living for the Gospel.
Greear directs his readers to rediscover the beauty of the Gospel through what he calls "The Gospel Prayer." This prayer breaks down into four parts: the first two portions help focus our minds on what God has done for us, the third part focuses on our response to what God has done, and the fourth portion directs us to how to reach out to our communities in faith. But instead of merely directing people to study the Gospels more, Greear encourages his readers to ask God to work on their hearts. Dependence on God is key, and Greear acknowledges that his book can only point you in the right direction.
If despair and apathy define your Christian walk right now, perhaps it is time to come face to face with the Gospel again. This book is a good start.