This passage pertains to fake, hypocritical persons who associate for a time in Christian assemblies of worship (tares that grow amongst the wheat); temporarily enjoying the blessings of worships and fellowship, but who were never truly saved and eventually fall back into perdition. Hebrews 10:39; I John 2:19-20
If they've been partakers of the Holy Ghost and they have been enlightened, then they know God and they have turned away. We won't know if we're eternally saved until we breathe our last breath on this earth, and only God can know who is and isn't eternally saved.
Jesus said, those who endure to the end, the same shall be saved.
We have to overcome as Christ overcame, we have to go through the fiery trials and be tested and we are to fight the flesh and deny Satan, and if we have the holy spirit he will strengthen us.
I can't believe that there are people who believe that we can wilfully sin and God will think that's ok and everyone who believes like them are going to heaven all the rest are off to hell regardless of how strong their faith is, or how they love and give their lives to God. That's just not true, sin separates us from God, and no one is predestined to be saved, we all have a choice and we all have freewill.
James 4
Therefore to him that knoweth to do good, and doeth it not, to him it is sin
Galatians 6
Be not deceived; God is not mocked: for whatsoever a man soweth, that shall he also reap. For he that soweth to his flesh shall of the flesh reap corruption; but he that soweth to the Spirit shall of the Spirit reap life everlasting.
James 1
Then when lust hath conceived, it bringeth forth sin: and sin, when it is finished, bringeth forth death.
You can't get any clearer than that.