We are all in need of salvation. The easiest person to deceive is ourselves. When we rationalize away what God says, this is what we are doing. God says that man has a sin problem, but man says that he does not. God is always right when he tells us that we have all sinned.
Death is a separation.
When we die physically, our body is placed into the grave, but our spirit is separated from our dead body and goes back to God, who gave it. In physical death, there is a separation between our body and our soul. This is a spiritual death, which is a separation from God in eternity for those who are lost. Since God is in heaven, and those who experience this spiritual death are separated from God, they cannot go to heaven. This leaves only one place for them to go, hell.