The author certainly seems to be implying that is the case. The problem is we have a very different experience. Many people who have been Christians have forsaken their faith and wandered off, only to become repentant once again later. Perhaps this description fits the Apostle Peter, who denied Christ three times and later repented and was restored.
So, if that’s not what the passage means, is there any other possible explanation? Perhaps.
If we deny Christ as the Savior, then there clearly is no other way into heaven. Therefore, if we deny Christ, it is impossible to be saved. Not impossible as in “you can’t repent” but impossible in the sense that “there isn’t another path that leads there”. Now, to be fair, the author does seem to imply that accepting and then denying Christ is grounds for permanent dismissal, but there aren’t other texts to support that idea, so we cannot make it a doctrine. At best, we should simply take our Christian walk very seriously, and do everything within our power to remain “in Christ”.
That includes making sure we are fruitful in our spiritual endeavors.
Blessed,
PR