The book of Hebrews is somewhat infamous for its warnings against falling away and willful sin. Hebrews 6:4-6 says that for those who have been enlightened (and so forth) and yet fall away, it is impossible to restore them again. And Hebrews 10:26-31 says there is no sacrifice for willful sin, and it promises vengeance against those who count the blood of the covenant a common, unholy thing.
But chapter 2 shows the beginning of the path that leads to that fiery end. The verses here do not speak of outright rejection, but rather of drifting and neglect. It is a subtle process that involves regularly prioritizing things of lesser importance above the opportunity that has been opened to us. In time, and with a continual focus on lesser things, faith begins to wane and one's spiritual strength is sapped. A callous forms on the heart, such that God's word can no longer get through.
The falling away and willful sin, then, are the late-stage result of a person routinely prioritizing something - anything - above God and His message. Through his or her own training, the person becomes essentially unable to make the right choices, and willful sin is the result. The heart becomes so calloused that it no longer cares what God says or thinks. But it begins with drifting and neglect.
Some commentators dismiss this passage because it is in a book called “Hebrews,” and they say it is only relevant for Jews, not for New Covenant believers. But notice that this describes people who have received the light of God’s truth and His Spirit.
Notice also that it does not say it is impossible to fall away, but rather that if they fall away—if they commit apostasy, or deviate from the faith and turn away from their allegiance. It says it is possible to choose that, and those who do cannot be brought back to repentance. They have publicly repudiated the Savior with their choices. The author says there is no coming back. In this way, our lives are not like gamebooks or video games, where we can start over if we reach an end we don’t like. We get one opportunity.
Matthew 24:13 tells us that those who endure to the end will be saved. A lack of total commitment has terrible consequences. As Luke 9:62 says, no one who looks back is fit for the Kingdom of God. If people fall away after receiving God's Spirit, they will not repent.
The word "impossible" is used there. That is a very powerful, strong word. What a terrifying thought to consider. If they know Christ but return to the world, their end is worse than the beginning, as the apostle Peter informs us in II Peter 2:20.
