This is a deeply spiritual question though it may outwardly seem like a generic one. To understand the answer to this question, it is important to know the difference between a spirit, soul and body. When Adam and Eve sinned and was moved out of the garden of Eden, they died a spiritual death. This is the meaning of why God told them that they would ‘die’ if they eat the fruit from that tree. Obviously, Adam did not die and went on to live for hundreds of years; so, what did God really mean by saying ‘die’. It is not physical death but spiritual death. This is the reason why we all are in need to be born again to inherit the kingdom of God; the spirit reborn in us is the one that works closely with the Holy Spirit to keep us close to God. The sin is passed on because after what Adam and Eve did, we are all now born into this world with sin in our hearts and mind. As we don’t teach a child to be greedy and wanting more, it just naturally comes when he/she feels selfish and does not want to share her/his things with siblings or other children. So are many other sins that are natural in us that the enemy uses to keep us away from God. We live in our body and we are tuned to just follow the desires of the flesh. This is why when we are born again, we need to start living in the spirit as emphasised by Paul in the New Testament. When we live in the spirit, we are led to follow God’s commands and are able to fight against the needs and desires of the flesh. Hence, staying away from sin.