For me it was a gradual realization...
- When my daughter was getting ready to go to pre-school, I realized how angry I still was at not being allowed to do anything I excelled out (sports or academically) during my lifetime, and I wasn't going to do that to her (nor was I going to force her to place literature with her teachers and everyone else).
- I tried to research the "creation book" and found other sources that didn't agree with the book's interpretation of carbon dating. Evolution made more sense.
- I read Mankind's Search for God and came to the conclusion that Taoism made more sense to me than the "garden path" argument for JWs -- they never did use that book for Book Study did they?
- A really major depression that took several years, lots of therapy, and the realization that dying at Armageddon couldn't be any worse than what I was already experiencing, and that going to the KH was a core reason I was experiencing panic and anxiety attacks.
I "faded" away, became inactive, told my family this is how I felt and came the realization that one of my core values was "live and let live". They can all be JWs all they want, but I expect to be respected as the intelligent human being that I am, who is capable and has the right to think, feel, and believe however I want to.