I think itsallgoodnow has it right.
The brainwashing began even before the Bible study started, while the JW's still giving you their 'sermon' and reading Rev 21, and the 'hook' is paradise.
As soon as you start thinking, "It would be really nice if it was true," they've got you. Thereafter, your critical thinking is on hold, you WANT it to be true, so you ignore any doubts you may have had and convince yourself it MUST be true.
After all, look at this neatly dressed, very sincere JW with the nice books with pretty pictures of lions and lambs and baskets of fruit and picnics and a beautiful garden with a lake at the bottom and lots of quotations from the Bible and they're not asking for any money...
After that you're putty in their hands. You've forgotten the old saying: i f it seems too good to be true, it is too good to be true.