2 Corinthians 13:5 "
Examine yourselves, whether ye be in the faith; prove your own selves.
2 Peter 1:10 "Wherefore the rather, brethren,
give diligence to make your calling and election sure: for if ye do these things, ye shall never fall:
1 Coritnians 9:27 "But I
discipline my body and keep it under control, lest after preaching to others I myself should be disqualified"
Jude 1:24 "
Keep yourselves in the love of God, looking for the mercy of our Lord Jesus Christ unto eternal life."
It's the Christians role and responsibility (not God's) in his own salvation to examone himself, to give diligence, discipline himself, to keep himself.
1 Coritnians 15:2 "
By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain"
Those Christians who do not examine themselves, do not give diligence, do not discipline themselves, etc will fall from faith and become lost therefore they would have "
believed in vain". A person who had never been saved/never really believed cannot have beleived in vain for they never have believed.
So the issue is NOT about those who never believed, were never saved but about those who actually did believe, saved but fall away therefore believed in vain.
Let that therefore abide in you, which ye have heard from the beginning. If that which ye have heard from the beginning shall remain in you, ye also shall continue in the Son, and in the Father."
1 John 2:24. Again, if the Christian does not allow the word of God CONDITIONALLY CONTINUE within him whereby the Christian does not CONDITIONALLY CONTINUE to believe.....he will fall away, he will NOT continue in Christ.