I John 3:4-6 Those who sin are opposed to the law of God; for all sin opposes the law of God. And you know Jesus came to take away our sins, for there is no sin in him. So if we continue to live in him, we won't sin either. But those who keep on sinning have never known him or understood who he is.
We must let these verses penetrate deep into our souls. We must understand what God is saying to us about sin. Sin does matter. Sin is not something we can ignore. We must take it seriously. It is what Jesus died to take away from us. When we excuse ourselves when we sin and pretend like it's no big deal, we are in essence saying that Jesus' sacrifice for our sins isn't that big of a deal. We are negating His death. Sin is what put Jesus on the cross. He didn't die for His sin, because He had no sin in Him. He died for our sin, because there is a ton of sin in us.
A true child of God does not continue to live in sin. We do sin, but it is not our normal way of living. We resist the temptations to sin. We deliberately say no to sin. We deal with sin when we fail. We understand our need for repentance. We are sensitive to our heart's need for holiness and seek Christ's forgiveness. We raise the standard of our hearts according to God's Word and strive to live by it. We are uncomfortable in the presence of sin. In other words, sin does matter to us.
If you have accepted Christ as your Savior and you are continuing to live in sin, you are only kidding yourself. You are not right with God. You don't know Him or understand Him. Jesus came to change us from a people who don't know God into a people who do know Him. And, if we truly know Him, we will become like Him and live in holiness and not sin.