The One God over everything is reflected by all people in the universe... even though many of them don't understand that the reflection of God is in them.
Bible writers were people God directed to do the writing for Him. The people He used were honest people who understood that God existed. They also believed Him.
Childhood is the best time to learn Bible religion. Why? Because embedding the truth of the Bible into children keeps them faithful to God all their lives... often even when they have many doubts.
You missed the top reason why the best sanity is to believe what God says. It's so that you can be saved for Heaven. You personally need to do a self-check, and ask why you are pointing yourself towards Hell.
If you were a psychiatrist, you might be able to help yourself... not that you would, any more than most psychiatrists.
