Also, Sabbath for us has a new meaning...
While Jews rested on the Sabbath because God rested on the Seventh Day, we rest (and are supposed to focus on our faith, like Sunday) because God himself rested in the Tomb on the 7th Day. It is in anticipation that we rest on the Sabbath, in anticipation of the resurrection of Christ, the rising of our God. At his eternal victory over death. We don't rest on the Sabbath due to an adherence to a law fulfilled by Christ, but rather it's because of Christ himself that we rest.
The law was simply in place for man. It is what we needed until God himself became man to save us. The law wasn't bad, man's abuse of it was. We have not forgotten the law. It's just been completed. It was simply a preparation for the coming of Christ. Mankind was prepared for the coming of God, I think we can think of the law as kind of like a fast. The fast exists for us so we can prepare ourselves for the end goal. When we reach that goal, do we still fast, or do we feast?
In the same way, is it right to adhere to a law that was in place to prepare man, when Christ has already come and God has manifested himself among us?
The law pointed to Christ. We no longer offer blood sacrifices, because those simply prefigured Christ's sacrifice. Now we offer the ultimate bloodless sacrifice. We no longer worship solely on the Sabbath in anticipation of the Lord's resurrection, because Christ has risen and we now worship on the mystical 8th day, the Lords day. The day he vanquished death itself.
Christianity isn't in opposition to Judaism, nor the New Covenant in opposition to the Old, it's simply a fulfillment and the proper continuation of it. As Christians, we are the successors to Abraham, to Moses, to David, to the Prophets, to all the ancient Hebrews, Israelites and Jews. The Church has remained the same, always, Ancient Israel has just been fulfilled in the Church, not replaced by it.