Psa 130:3 If thou, LORD, shouldest mark iniquities, O Lord, who shall stand? 4 But there is forgiveness with thee, that thou mayest be feared.
7 Let Israel hope in the LORD: for with the LORD there is mercy, and with him is plenteous redemption.
The work of the cross is so complete, so overwhelmingly efficacious that the believer can totally rest in the forgiveness made possible by Christ's sacrifice.
It really has nothing to do with us, and everything to do with Him. If we are His, we are forgiven, comprehensively. Our sins, past, present and future, are obliterated by the blood of Christ.
This is just another thing that causes us to shout, what a wonderful God, what a blessed plan, what a glorious Savior!