What was Napoleon Hill's Secret?

Factual Questions
1

I recall reading Think and Grow Rich, and I remember his speaking of some mysterious secret, that I never found out. IIRC, he said I would know it by the end of the book, and I never new it. I can’t recall if I read the book all the way thru, but I think I did. So, does anybody care to rat him out?
Thanks,

hh

2

“What the mind of man can conceive and believe, it can achieve” is about the extent of it. What great insight does any self-help guru really have?

3

Hmmm…good point.
Except, maybe: “There’s one born every minute.”
Thanks,

hh