I was raised in a Catholic household in a Catholic parish with next to no interactions with non-Catholics. Nowadays, I abhor Catholicism even more than materialism. I think it'll be some combination of cathartic for me and interesting for someone else to write up the story.
I was never a very good Catholic. Me and my siblings had what I believe is far more than an average amount of physical fights, and I always stood by my actions. I was a retributionist from my first breath and never fell for "turn the other cheek" or "it doesn't matter who started it" (the former I didn't hear until I was older; the latter was raised verbatim regularly).
My family wasn't very devout during my first twelve years (we had never prayed the Rosary, and I think we started going to confession when I was about ten). So although I outright believed in revenge, I was never really pressed about it.
I think things started to change when I was 12. I figured out the free will refutation of the materialist account of the mind. It took me about 5 seconds after noticing it to be fully convinced, and I've never once doubted it after that. In fact back then something incredible happened: I convinced my younger sibling. It was even easy. Of course, I was the only one who stuck with that during later years. Needless to say, I drew immense hostility from the others for that as soon as each one found out.
I think I was still 13, but I might have been 14, when things really got moving. My older brother left the church. During the timespan both my older siblings had moved out and there wasn't as much fighting, so I didn't view my siblings as enemies anymore. That was the first time it really occurred to me that there was such a concept as not being a Catholic. Although, my older brother hadn't left because of disagreements but because he "didn't want to do what God says", this was still a religious awakening that had me realize that being a Catholic, let alone a devout one, was both important and not a given.
Probably as a result, I began to think a lot more about my religion, and run across more of the errors in it. As with retribution, I dismissed each error I found in church doctrine as "not really church teaching, it must just be misunderstood and the Catholic doctrine is actually supposed to be what I believe" (I did actually find a Catechism paragraph that made this argument relatively defensible for retribution). But most of the times I knew on some level that the Catechism would tell me I was wrong and so I convinced myself I didn't need to consult it because I was so sure. When even that became untenable, my self-deception went as far as me deciding the Catechism in my house was written by bad bishops in the employ of the secular, anti-Catholic conspiracy, and essentially that I was the only real Catholic in my life. Ironic.
I had a phase where I gradually noticed that I didn't feel allied with other Catholics. When someone identified themselves as a Catholic, I thought "Right, another fake Catholic who believes Satan's lies". I noticed that I felt more comaraderie with atheists than with Catholics. I felt like an infiltrator at the Mass, surrounded by traitors and led by a traitorous priest.
Original sin was the doctrine that pushed me over the edge. I wasn't responsible for Adam and Eve's sin, there was no reason baptism should be necessary to cleanse me of it, and I was done deceiving myself. The Catholic religion really was wrong.
Even that wasn't sudden. I did have a phase of uncertainty, where I noticed how guilty I felt praying with other Catholics, saying words I didn't believe. But I couldn't deny it for more than a day after that. The other Catholics weren't the traitors. I was. And I stood by it.
One image I'll always remember was the moment where I think I really crossed the border. I was looking into a heavy rain in my familiar yard, and without Jesus, the same tree I thought was beautiful before now looked hostile. I was a child who ran away from home that day into a world I knew nothing about, and without a perfect being holding my hand, the world was a frightful place.
And for the first month after I left Catholicism internally, I still told myself that it had to be close to the truth; the truth still had to be related to Judeo-Christian history. Of course it was easier to think the arbitrary beliefs and customs I'd spent most of my life believing in weren't without any basis in the truth. I did a lot of research on the SSPX in the hopes of finding no doctrinal error and joining them, and even a little bit of looking into Islam. Surprisingly, it didn't really occur to me to learn more about Judaism. But now that I was free of the mental chains of Catholicism, I was rapidly throwing out more and more of their beliefs that I had only held onto because I had to, and the SSPX and Muslims seemed like mere variations on the amalgamation of shit I was raised with. I knew after a while that no prominent religion was right.
And for multiple years after that I kept my apostasy a secret from my family. I was so terrified of the consequences. I thought they'd see me as an outcast from the family as well. Would I be able to have a conversation with them anymore? How would they react to a second son of theirs leaving the church, and instead of being sorry like the first one had (I don't know if he came back before or after this), I'd be telling them I was right and they were bad people for not leaving too? How much arguing would I have to do? Although I stood by my beliefs without any doubt, I knew I couldn't explain them well under pressure, and besides they'd be disgusted no matter how well I justified myself. I still valued my relationship with my older brother and didn't want him to turn hostile.
Those entire years lived under a false identity are one of the biggest regrets of my life. I considered it a sin to go to Mass and pray to the god who didn't exist. I actually kinda considered it sacrilege. How much did I miss out on by lying to everyone? I had to avoid religious conversations for fear that one of the contradictions of Catholicism would be exposed and I'd have to choose between profaning my belief in reason and conscience or coming out. I knew it was my duty to tell the truth, and I considered it a sin every day I didn't, but, I wasn't brave and I had come to terms with that.
One of the factors that helped motivate me to come out was realizing how many hours I must've wasted going to Mass and saying the Rosary with everyone (we'd gotten more devout at some point here and started praying it most days). Thousands? What could I have accomplished if I had been honest from the start? With all that freed time, how many words of novels could I have written? How much could I have learned in the way of useful skills?
Finally, I came out to my family and the reaction was, to put it how I felt at the time (and still do), insultingly unimpressive. There was barely any reaction. No one even tried to argue with me. I thought at least my older siblings would've. Did they think I was too irrational to be convinced, did they know their beliefs were irrational, or did they just not care about their religion?
Regardless, what I'm certain of is that Catholicism is a horrific religion with almost no truth in it, that deceiving yourself is always wrong, that deceiving others is also wrong, and that telling the truth makes you more powerful in multiple ways. I've also learned a lot from my experience about the malicious genius of Catholicism and how cleverly this religion manipulates and impairs the minds of its followers. I'll write more about it some time.