“Luther preached that there was nothing more important for a person than to see that he or she could contribute nothing whatsoever to one’s own salvation. We can be fully accepted and counted legally righteous in God’s sight through faith in Christ, solely by free grace. To understand and grasp this is to finally know freedom from the crushing burden of proving yourself – to society, family, other people, or even to yourself. It means freedom from fear of the future, from any anxiety about your eternal destiny. It is the most liberating idea possible and it ultimately enables you to face all suffering, knowing that because of the cross, God is absolutely for you and that because of the resurrection, everything will be all right in the end.
The belief that we are saved by our virtue, the state of our hearts, or our good works injects a heavy layer of uncertainty and insecurity in our lives. If God’s treatment of us is conditioned by the quality of our lives, and the quality of our lives is always far from perfect, then we can never be sure he is completely for us, loving us. To escape this uncertainty requires that you dispel any illusion that through your wisdom and strength you can either create a safe and good life for yourself or put God in the position of owing you such a life.”
Tim Keller in Walking with God through Pain and Suffering