In this part of the letter to the Hebrews, Paul points out the difference between the work of Jesus and the work of the priests of Israel. Every year the priests offer up sacrifices for the sins of the people. Jesus offers himself up once. This is because he is the perfect priest who himself is also the offering. The priests of the Law are only men like us and after they have made sacrifice for sin they go out and sin again--as we all do.
Paul quotes from the Old Testament: "I will put my laws into their hearts and write them on their minds. I will never call their sins to mind or their offenses."
When Jesus forgives sins they are gone forever. Why do we go on bringing up our sins in our head, punishing ourselves over and over again. Jesus has forgiven our sin. What an insult for us to go on punishing ourselves over sins that are already forgiven. What does Jesus have to do to prove to us that he forgives us? Die for us!!