Hebrews 8: A New Covenant

But God found fault with the people and said: “The time is coming, declares the Lord, when I will make a new covenant with the house of Israel and with the house of Judah.
It will not be like the covenant I made with their forefathers when I took them by the hand to lead them out of Egypt, because they did not remain faithful to my covenant, and I turned away from them, declares the Lord.
This is the covenant I will make with the house of Israel after that time, declares the Lord. I will put my laws in their minds and write them on their hearts. I will be their God, and they will be my people. - Heb. 8:8-10 NIV

We all prove, time and time again, that it is impossible for any of us to keep the terms of the covenant with God without the cross, without Christ's blood sacrifice.  Just like Israel, we are unable to conform to God's laws on our own.  He has set the bar too high.  Not because he doesn't love us, but because he has always loved us and wants us to be complete in him.  The only way to be all that God created us to be is by surrender, surrender to the saving power of the gospel.  Through Christ, the covenant has been sealed.  It is an unbreakable covenant, made possible only by the blood.  Just as the sacrifice of the priests made atonement for the sins of the people and renewed the covenant with Israel, Christ's sacrifice secures the permanency of the covenant for us.