Deuteronomy 6:17 Ye shall diligently keep the commandments of the Lord your God, and his testimonies, and his statutes, which he hath commanded thee.
Our response to God’s Grace and Salvation is to do what He says, keep His Commandments. God loves us so much that He wants what’s best for us, and so He gave us the Ten Commandments for a blessed life. “If you do them you will live in them.” Blessings and curses come to lives and families according to how closely we keep the Law. A Blessed Life is a natural result of obedience.
Unfortunately, sinners cannot keep the Law perfectly, and life suffers as a result. But fortunately, Jesus kept the Law perfectly for us. Therefore, the righteousness of God is granted for believers in Christ. Thus we live in two worlds: saint and sinner, old man and new man, flesh and spirit, the world and the kingdom, life in the midst of death. Life, righteousness, peace, love, joy and hope live alongside death, pain, misery, hatred, and sadness.
We do well when we look at the things of God that are not seen, when we focus on the things above, when we seek first the kingdom of God and His gift of righteousness. Believing in Jesus is keeping the commandments and receiving forgiveness for failure. Diligently simply means keeping your eye on the ball, paying careful attention to Law and Gospel.