Sad indeed is it to witness so many young professing Christians just starting out on their arduous journey to Heaven, being told that the words "He that endureth to the end shall be saved" apply not to them, but only to the Jews; and that while unfaithfulness on their part will forfeit some "millennial" crown, yet so long as they have accepted Christ as their personal Savior, no matter how they must indulge the flesh or fraternize with the world, Heaven itself cannot be missed. Little wonder that there is now such a deplorably low standard of Christian living among those who listen to such soul-ruinous error. Not so did teachers of the past, who firmly held the eternal security of Christ’s redeemed, pervert that blessed truth. No, they preserved the balance, by insisting that God only preserved His people in the path of obedience to Him, and that they who forsake that path make it evident that they are not His people, no matter what their profession, and no matter what past "experience" they had.
I suggest reading the whole post (and purchasing Pink's commentary on Hebrews for that matter).