Auto-suggestion

Napoleon Hill calls this chapter the "keystone to the arch of this philosophy". This chapter is where the money is.

In this chapter, you are instructed to read this chapter aloud every night, until you are sure that the principle of autosuggestion will work for you.
This is interesting, because I think its so easy to read something, nod your head, say "yeah that makes sense" and then apply nothing of what you have learnt. There's also a difference between saying "yeah, that makes sense" to actually believing that this will work for you.

Which is the reason why, I think, it is fully worth following his suggestion, and reading the chapter out aloud every night. I didn't follow this advice until well past my 12th reading of the book, and I have to say, without doing it, it is very easy to just theoretically agree with what he says, but not truly, emotionally believe it.