Christians often make the mistake of thinking that the gospel is just for lost sinners in getting them saved and then after that it's pulling oneself up by one's bootstraps so to speak to attain holiness (sanctification). The truth is that Christians need the gospel every day. It causes us to be humble and not self righteous. It causes us to have confidence before God based on what Christ did and our being "in Him". We need to preach the gospel to ourselves every day. It is the power of God. We are not on a self-improvement program that combines grace and law. Paul was misunderstood when he preached the gospel as being soft on sin and sinners. He wasn't. Preaching law does not empower anyone to become holy. We are holy in Christ (our new-born spirit man) and we manifest that holiness by focusing and identifying with that new nature and spirit. It works itself from the inside to the outside.
Here is a wonderful video that discusses these points from Tullian Tchividjian's blog. It is only about nine minutes long. Enjoy
http://thegospelcoalition.org/blogs/tullian/2012/06/22/the-gospel-for-christians/
