For me the big thing was realizing there was no God. ( I never believed in 1914 since the reasoning was so convoluted and unconvincing) For years, even as a pioneer, I had interpreted the figure of the Devil as a melodramatic literary persona and not a real thing.
I was in my office at home one day reading the philosophy of Kierkegaard and it hit me: ok the devil is fiction... but neither is there a God. The whole religion thing functions whether god exists or not. The Watchtower and all religions are a sham. This was the turning point from which no return was possible.
I was glad I had had the realization but worried for my family. I faded successfully without immediate reprisals, then it was announced that I was no longer one of Jehovah's Witnesses but was then treated as a disfellowshipped individual. In my family's eyes I had joined the devil's party. My wife had moved from normal "other sheep" mode to "anointed" mode and had a nervous breakdown, the children were badly affected psychologically and the marriage was over.
Even with those dire consequences, I would rather live according to my conscience as a free agent than be beholden to the Watchtower's insidious cult regime.
One of my sons has left the borg and is enjoying an adventurous life, two offspring yet to leave.