God is Sovereignly in control, meaning He has total control. Remember that you do not live anymore. Christ is living your life for you. You don't bring cancer to yourself by anything you do or do not do. In the same manner, you cannot heal yourself by anything you do or do not do. It is totally in God's control. Have you ever heard of someone who had lung cancer but did not smoke? Whether you live or die of cancer you are healed if you belong to God. Your own human efforts cannot heal you, only God can. Praise Him with all that's within you.
