If one believes that one is saved by faith, then it follows that what damns is lack of faith, right? Then how does sin play a role? If one has saving faith and yet continues to sin, is that person damned or saved? If sinlessness is a prerequisite for entering heaven, then who may enter through heaven's gates?
I don't think being sinful or not is the deciding factor, Its wether you have faith in Jesus and repent of your sins. The difference between you and me sinning is your sins are forgiven (presumably) and mine aren't. Don't forget we all fall short in the sight of God.