Eph. 5:8-9 ...For though your hearts were once full of darkness, now you are full of light from the Lord, and your behavior should show it! For this light within you produces only what is good and right and true.
Your hearts were once full of darkness, you just couldn't help yourself. Once you lived in sin, a lot. You did it naturally. It was the desire of your heart. You weren't ashamed of what you did. In fact, you considered those who didn't sin weird. You lived and enjoyed the momentary pleasures sin brought to you. Your heart was full of darkness. There simply wasn't any room for God's light to shine in.
But, Jesus came knocking on your heart's door and you let Him in. Your eyes were opened and you came to realize that you could no longer live in the life of sin. Jesus showed you the consequences of sin and you no longer wanted it. Your desires changed from wanting to sin to not wanting to. The more you let Jesus shine His light on your soul, the more you wanted to please Him. Your heart became full of light instead of darkness and there simply was not any more room for sin.
And, this is the way it should be. When we walk in the light of God's written and living Word, the more our behavior changes. It becomes obvious to all by the way we live and talk that we are indeed children of God. God in us produces only that which is good, right, and true.
If you are struggling with sin in your life, the problem is not the Lord's inadequacy to help you or change you. He is more than able to do that which He has promised! The problem is your willingness to let Him change you. In some way you are holding back from the Lord control over your sinful desires. We are all guilty of doing it, but that is no excuse for sinning. We must let the Lord access to every room of our hearts so that His light can dispel the darkness.
We must strive to resist sinning by letting the Lord be Lord of all of our lives. He cannot be your Lord until he is Lord of all your heart. Will you let Him by Lord?