The great British preacher, C. H. Spurgeon, said, "What is the value of the grace we profess to receive which leaves us exactly the same kind of people as we were before we received it? An unholy life is an evidence of an unchanged heart and an unchanged heart is an evidence of an unsaved soul."
Some people have an image of God and His laws in which they believe that if they fall short, God is going to punish them. And while it is true there are repercussions for disobedience to God, we should not merely obey God because we are afraid of what will happen to us if we don't. The higher motive, the better motive, and the purer motive is to obey God out of love for Him. In recognition of all that God has done for us, we should now want to reciprocate and show Him our gratitude by obeying Him.
Jesus said, "If you love Me, keep My commandments" (John 14:15). Why? Because as James tells us, faith without works is dead (see James 2:17). If someone says they have truly committed their life to Christ, if someone says they really love God and yet live in open sin, then their love for Him seems high unlikely.
I am not suggesting that a Christian will not violate God's commands. I am not even suggesting that we will never fall short of them. But what I am saying is that if we are really children of God, we should be seeking to lead lives that are pleasing to Him.