This cannot be said often enough. We are not sinners because we sin, we sin because we are sinners.
We are not good people, who occasionally "mess up", and who are tagged forever as sinners because of one mistake.
We are sinners, all of us. Some of us have our sin under some control (usually, just the external manifestations, the internal rages away).
We become quite adept at rationalizing our sin. I need it. Everyone else does it. It's not really that bad. As long as no one gets hurt. Etc.
This process hardens our hearts. It is the "hard path" and "rocky soil" spoken of in the Parable of the Sower (Luke 8:4, Matthew 13:3). We become immune to understanding the things of God.
The solution is the application of God's Word; sharper than any two edged sword. The Ten Commandment have been compared to a sturdy shovel, breaking up the rocky soil and preparing it to receive the seed of the Good News.