He says He will and He means what He says! we are assured of this because of the great atonement that took place when He cried from the cross:"Lord forgive them!"
Thoes words erased all of our sins to the extent that they are not found in the mind of God. God sees the believer through Jesus Christ, as He saw Adam in his purity before the fall. But even more than that, the believer now has the righteousness of God while Adam only had the righteousness of man.
Our great and might God will not remember our sins and therefore He will not Punish us. His love for us will remain great. A debt forgiven is no longer a debt. This is exactly what happens when our sins are forgiven.. God forgives the iniquity of His people when our hearts are broken within us and we morn over our transgressions and shortcomings.
Let our minds be comforted that the lord will no longer remember our sins. Let this comfort cause us to hate sin. His great and complete pardon will cause us to never think of disobeying Him again!