I didn't really stay in "even when you knew it wasn't the 'truth'"
I was raised in the truth with strict parents and left school and pioneered, I left over 20years ago. When I stopped preaching, two things were involved. One, I couldn't preach something I was unsure of and the other was it occurred at a time in my life where it was easier to change.
There was a period where I tried to resolve the problem (doctrinal) that I had and thought things may change. This was about 2 years. Going in field service stopped immediately and meeting attendance became less frequent. At first, the meeting attendance diminished due to a change in our circumstances brought about by the 'problem' and later due to the reaction of the elders in taking six months to visit me although I had requested it.
Coming to a conclusion that it isn't the 'truth' isn't something I feel in a position to make.