Protestants emphasize the born-again experience. Once you accept Jesus as you Lord and Savior, you are saved forever. It's that moment of acceptance that counts. But for the Catholics, the born-again experience is an ongoing process. Scripture makes it clear that a disciple of the Lord is to shed his old self and be transformed into a new creature that's Christ-like. Since we'll never be able to reach the perfection of Christ, this renewal process must continue for our entire lifetime. One just doesn't become holy overnight.