"For by one offering He has perfected forever those who are being sanctified" (Heb. 10:14).
But how? Here's how…
Paul wrote to the church at Corinth to answer this. Since being "good enough" through personal effort is so futile (Rom. 7), only a transfer of account if ya will..from the righteous Person to a sinner like me could actually remedy the problem. Yep, "He made [Christ] who knew no sin to be sin for us, that we might become the righteousness of God in Him" (2 Cor. 5:21). How cool is that! The Cross fully appeased.
Though we've all sinned, God ain't mad at us. No need for wrath on us, and Christ's righteousness was attributed to us..if we'll each take it by faith.