I think the warning passages are directed to mostly Jewish people who are intellectually convinced that Christianity is true, but have not yet fully come to Christ in true saving faith. These are they who are in danger of falling back/away from Christ, with no subsequent opportunity for salvation.
We cannot save ourselves, and just so, we cannot keep ourselves saved--statically or dynamically.
VERY well stated.
The eternal security of the believer is an essential doctrine. If we believe that we can be saved through Jesus' redemption at the cross and then lost again, then what Christ did at the cross was no different, no truly greater, than the temple offerings of the priests throughout the old testament.
No, we canot save ourselves, or keep ourselves saved. If we accept Christ as our Savior, the seed sown begins to grow, despite ourselves, sometimes. I also think of the thief hanging on the cross who accepted Christ---what in the world could he possibly have done to "earn" his salvation after accepting Christ? Nothing.
That is not to say that we should ignore the Father's preferences for our lives (for Christ has fulfilled the laws), Christ's model for our behavior, or the Holy Spirit's leading in our minds and hearts. Paul speaks of how "we should then live."
The one missing out on a fulfilled and blessed life is the one who does not seek the Father's will. This "lack of action" on the part of the believer, however, does not trump Christ's action on the Cross.
Although the saved person may get to heaven, it shall be "as through fire." All his/her works shall be burned away and that person will have little or no reward once in heaven.
My Scriptures say there is only one unforgiveable sin: "do not GRIEVE the Holy Spirit." And if you think that grieving the Holy Spirit is "merely" being disobedient, or not acting properly, or not acting with the will of God, that these things preclude one from salvation and heaven, then I think that you'd have to lump in all of mankind, including the apostles, King David, etc., who have disobeyed, disbelieved, acted wrongly, thought impurely. Because their disobedience, the sins Christ died for, overcame Christ's powers to save.
I believe what Christ did at the cross is stronger than anything I could ever do to "earn" my residence in heaven; is stronger than anything I neglect to do to "keep" my residence in heaven; is stronger than anything I "work" to do to "prove" I should go to heaven. Because none of us "should" go there, no matter how many "good works" we do to "keep" ourselves there. All our works are as filthy rags."