Many believe and teach that once and individual is saved he cannot be lost. However, the Scriptures clearly teach that a child of God can forfeit his salvation and be eternally lost.
Many passages speak of the conditional nature of our future salvation.
The apostle Paul in warning the Corinthians against apostasy realized he too could fall away and be lost. Certainly, if there was a possibility for the apostle Paul to be rejected, then we too could be. Right after that statement he used the example of the Israelites who fell from God's favor by their disobedience and were not permitted to enter the promised land. These are solemn warnings against falling away and being lost. The Scriptures also speak of examples of those who did fall away.