Humankind was originally created without sin. Our first parents were made by God to have Original Righteousness and Original Holiness. This is what is meant when we say that we are created in the image of God.
Once humankind fell by believing the devil’s lie that we could become like God (Genesis 3:5), all that Original Righteousness and Holiness was ruined as the First Sin took root. We call this “Original Sin” which simply means we lack Original Righteousness and have the inclination to sin. When Original Sin took root in Adam and Eve it acted like a disease and was passed along just like all the other things we inherit from our parents. The complete harmony we once had with God became a complete disharmony and has been ever since. Because of Original Sin and the sins we've added to it, Scripture calls us blind to the will of God (2 Corinthians 4:4), dead in our trespasses and sins (Ephesians 2:1) and enemies of God (Romans 5:10). Being “blind,” “dead,” and an “enemy” of God puts us into an impossible position, for people who are “blind,” “dead,” and “enemies” of God do not love God, choose God or want to have anything to do with the Triune God. Original Sin does not mean we are as bad as we can possibly be. It means that each one of us is “tainted” by sin and that there’s not a part of us that isn’t touched and affected by it.
“Born again” Christians are likewise sinful. Believing, confessing, well meaning, God-fearing Christians also lack Original Righteousness and have evil desires and an inclination to sin (Romans 7:13-25 ; 1 John 1:8-9). During the days of the Reformation, the reformers put it this way: we are at the same time “saint” and “sinner.” Therefore the Christian life is a constant struggle against sin. It is important to note that sin is not driven out of us; rather, because of what Christ has done for us, our sin is not reckoned or counted against us. The Righteousness of Christ, given to the Christian, is what the Father in heaven sees and it’s because of Christ’s righteousness imputed to us, and not because of anything we’d done or any “spiritual improvement” that we've made, that we are counted righteous. In other words, we are counted righteous by a righteousness not our own.