In the story of The Prodigal Son, its not making the effort to turn your life around that saves you, nor is it living your life as perfectly in tune with his will as you can. None of us are saved by anything more than God's incredible gift of love. The difference between the end result for the two sons was pride. One son returned home full of humility. The other refused the gift out of self-righteous pride. God struggles to get through to a proud heart.
One brother - very obviously lost. The other brother - lost, but didn't know it! He thought he was saved! Food for thought...