Why believe the devil?

“Why believe the devil instead of believing God? Rise up and realize the truth about yourself – that all the past has gone, and you are one with Christ, and all your sins have been blotted out once and for ever. O let us remember that it is sin to doubt God’s Word. It is sin to allow the past, which God has dealt with, to rob us of our joy and our usefulness in the present and in the future.” —Martyn Lloyd-Jones