The 'once saved, always saved' is but a clever advertizing claim. One is 'saved' by constantly keeping faith in Christ. It's a process, a constant flow. If one loses faith, salvation is witheld, and the individual must seek to re-establish his faith so that salvation can once again be attainable.
Romans 5:1 - " Therefore, since we have been justified by faith, we have peace with God through our Lord Jesus Christ."
2 Timothy 4:7 - " I have fought the good fight, I have finished the race, I have kept the faith."
Hebrews 11:6 - "And without faith it is impossible to please him, for whoever would draw near to God must believe that he exists and that he rewards those who seek him."
Matthew 10:22 - " But the one who endures to the end will be saved."
Matthew 10:33 - " But whoever denies me before men, I also will deny before my Father who is in heaven."
Hebrews 6:11, 12 - " And we desire each one of you to show the same earnestness to have the full assurance of hope until the end, so that you may not be sluggish, but imitators of those who through faith and patience inherit the promises."
Faith can become weak, faith can be lost. The loss of faith, if permanent, equates into the loss of salvation.
Hebrews 10:26 - " For if we go on sinning deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins" Earlier, Paul described the lack [or loss] of faith as a sin.
Eden