Paul is not talking to saved but the unsaved here. He had a real problem during this writting with Orthodox Jewish infiltrators into the church.
These spies would claim to believe in the gospel and participate in believing in Jesus but on the sly, would tell others that to be saved they must come back to the Temple and participated in sacrifices.
Paul was explaining this to the real Christians, that it is impossible to fall away. This is one of the greatest supports for "Once Saved Always Saved."
It's not a matter of God pulling away ( he said he would never leave) but it is we who let our fleshy desires get in the way.
Paul was talking about those, in their mits, that weren't saved in the first place......these verses have put many a person into bondage of untruth!