What is the secret in Think and Grow Rich

> Hi I've read through Think and Grow Rich by
> Napoleon Hill, and I'm not sure what the
> money making secret is that he tells in
> every chapter of the book. Any ideas?

here is one answer i've heard of. the secret is
in the statement,

"what the mind can conceive and believe, it can
achieve."

but i don't really know if that this is really
the secret or not.