Since all the unsaved already have their souls lost, the scriptures are not about the unsaved but the saved. All Christians have a saved spirit by faith in the Lord Jesus’ death, burial and resurrection. However, their souls still need salvation, this mystery is revealed in the seven feasts of Israel.
The Lord Jesus warned his disciples of losing their souls for three reasons. The first is because they did not deny themselves, meaning the pleasures of sin that they were doing while unsaved it would appear they never overcame these sinful pleasures but kept on fulfilling them in their lives. The second reason stated is that the disciples may not have taken up the cross; this has the same meaning to it only it also includes fasting and praying as a part of crucifying self. Finally, the Lord mentions to follow him, this has to do with the commandments that are written in the Word of God, meaning these disciples were not keeping the commandments.