I think that even "good" JWs can't follow all the rules. They just want to follow the rules, and pretend they're following the rules, and so everyone agrees that they're good JWs. After all, if they all agree on something, it must be true, right?
I certainly think this describes my mother. She can't possibly follow all the rules--if she did, she wouldn't have her children and grandchildren in her life at all, and her health would be even worse than it is. But she wants to follow all the rules, and she pretends that she's following all the rules, until she has even herself convinced that she is following all the rules. The human mind is a magnificent thing; its powers of delusion are remarkable.
The problem arises when some either can't (and many have described abusive situations that were simply unlivable) desire to and pretend to follow the rules, or won't (as in, "did the math and became apostate") desire to and pretend to follow the rules.
No one can follow the all the JW rules, not even the best little goody-two-shoes-I-wanna-be-an-elder-or-at-least-an-elderette JW. The difference is that some pretend they do, and thereby allow the organization to control them by controlling both their behavior and their self-image (as so aptly pointed out above).
Jankyn