Exactly:
"Not with the blood of goats and calves, but with His own blood He entered the Most Holy Place once for all, having obtained eternal redemption" Hebrews 9:12
"not that He should offer Himself often, as the High Priest enters the Most Holy Place every year with the blood of another" Hebrews 9:25
So Christ was offered once to bear the sins of many" Hebrews 9:28
Believe me, going to Mass every Sunday won't sanctify you. Praying the rosary, receiving the sacraments... they won't sanctify you either! Paul tried to follow the Law and found out he could't so he cried in despair "O wretched man that I am! Who will deliver me from this body of death?" Romans 7:25
The answer? Read Romans 6, the whole chapter. It has all the answers.
Preaching to the choir :)