1John 5:13
"These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life..."

So many people walk this earth knowing they are going to die yet don't have that assurance that heaven will be their home.

How does one sleep at night thinking they could wake up in hell?

I suppose it would be called "blissful ignorance" or "prideful thinking" to all those who reject Christ until the Great White Throne Judgment. Then it will become reality to them and not nonsense! Unfortunately it will be too late for them.

It's sort of like jumping out of a plane for fun with a faulty parachute ... it's not the fall that kills you; it's that sudden stop! The pleasures of this world is short lived but burning in hell has no end.