God and the law
But I don't think this is simply about the law. Rather it is about God who is the author of the law. God made the law to reveal His heart - he doesn't want everyone to die because of selfishness. The law is about God.
The law is about Jesus, the Son of God who perfected the law in himself. He is teaching us the law of love, "Love one another as I have loved you." Now the law seemed stricter, but it made more sense because the guiding post of the law is love; and love is perfect only in Jesus.
Finally, in Jeremiah 31, 33: "The law shall be written in your hearts." The Holy Spirit which is poured on the apostles on Pentecost is the same Holy Spirit guiding us right this very moment. Thus we shall know how to live the law because it is planted deeply in our hearts.
If we think we're already following the law, why do we rebel against God, thinking that our plans are better? If we think we know Jesus, why don't we make our daily sacrifices to save others? If the law is written in our hearts, why are we not united as one Church? It's simply because we haven't loved God enough.
Let us remember, every observance of the law should always lead us to a deeper, closer relationship with the Author of the Law, God, in Jesus, through the Holy Spirit. This should be enough to change our lives from selfishness to self-giving.