Wanderer - I'm glad you post these type of threads, it opens up discussion on a subject that both those who have already left and those who are contemplating can relate to and think about, keep it up please.
As far as your main question (the topic) I feel from my own personal experience, that to devote yourself to a religion like this that requires you make a stand against non believers (non JW's) in many situations - example: holidays like xmas, to devote much time and effort to it, that it simply must be right. The indoctrination has been leading your mind to not accept the possibility that it could be false or a lie. Any area's of doubt can really shake a person until they regain their JW mindset and push it away into the deepest part of your mind. It doesnt work on a logical thought process, but rather a conditioning, that replaces the right conclusion with the one the WTS wants you to think. When I am able to speak to current witnesses and ask them questions a mental wall comes up when something that could challenge their beliefs is discussed. It seems to me to be a mechanism, that automatically takes over to keep the person 'safe' from reality. It is also about dependance, like a habit or drug that one can simply not function without, and the fear of losing it is too much for them to consider.
CS 101