Context makes such a difference. Without a proper understanding of the context of a situation it is hard to draw the proper conclusions. For example, what conclusion do you draw from a situation where a man is holding a knife to another man's throat? Is it a safe situation or a dangerous one? Well, that depends if the man holding the knife is a murderer or if he is a doctor about to perform a life saving operation. And without a proper understanding of the context of the situation you may make the wrong conclusion.
This is the purpose of the Law, it helps us to understand the context of our lives. The Law was given to man as a mission IMPOSSIBLE. Not difficult, or unlikely but IMPOSSIBLE. For the Law was not given for man to succeed, but instead for him to fail. That's right, God gave the law, not as a method or formula for him to follow that he might find success, but so that man would fail and fail miserably (see Romans 5:20). For the Law demanded that man be perfect, all the time, as perfect as God in Heaven is perfect (see Matthew 5:48). Why would He do that you ask? Because it is only in our failures that we come to discover our need for a saviour. If we could make life work on our own, we wouldn't need Jesus.
It might help to think of the Law as a spiritual x-ray machine. An x-ray machine can be used to discover/expose, a hidden tumour, a broken bone, or something else that is wrong that might otherwise not be easily seen. Similarly, the Law exposes the sinfulness of the unbeliever (see Romans 7:13) by setting the standard, a standard so high and so perfect we discover how rotten man is apart from God.
Look how Paul puts it in 1 Timothy 1:8-10,
"But we know that the Law is good, if one uses it lawfully, realizing the fact that law is not made for a righteous person, but for those who are lawless and rebellious, for the ungodly and sinners, for the unholy and profane, for those who kill their fathers or mothers, for murderers and immoral men and homosexuals and kidnappers and liars and perjurers, and whatever else is contrary to sound teaching."
But here is the key. Just as you would never expect the x-ray machine to heal a broken bone, you do not use the Law to deal with your sinfulness. This is why we have the cross. For on that cross not only were are sins forgiven and taken out of the way, but so was the sinner. The sinner, your old man, the you and I we used to be when we arrived on planet earth, was crucified with Christ and no longer lives.
So what then keeps us in check? Is it not still the Law? Nope. Now it is the very presence of Jesus Christ living in us. For as we trust in Jesus to live is us each moment, we can't help but fulfill the righteousness of God which was demanded by the Law. This is probably best summarised in Galatians 2:19-20,
"For through the Law I died to the Law, so that I might live to God. I have been crucified with Christ; and it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself up for me."
So keep the Law in its proper context. It has a great purpose, but only for the unbeliever - to expose the need for their salvation from themselves. But once they have discovered the problem of their sinfulness, the Law can help them no more. Then, all they need is Jesus and the work of the cross.
In Christ who is our Life,