I never lost what I never had.
My parents were from mixed religious backgrounds. My father’s family were Catholic, of the flavor that they believed anything a priest told them and had crucifixes all over the house, but I don’t know how much time they actually spent in churches.
My mother’s family were Lutherans, of the flavor that they went to church like clockwork – every Christmas and Easter. They occasionally mentioned God and every so often threw in a half-assed, “God is Great, God is Good, Come on mama, bring on the food” grace at dinner.
It was always at loggerheads, so I’m told, and so I recall. I can remember the first butting of heads when I was around 5 and my father’s family insist that I be baptized. My mother begrudgingly went along with it. I remember being petrified. I had no idea what being baptized entailed. But I can clearly recall thinking it sounded alot like “hypnotized” and all I knew is that I didn’t want anything done to me that ended in “-ized.”
So anyway, not long after that, I was 7, the family moved to a predominantly Catholic rural town. My father had long ago given up anything religious* and my mother was more than happy to ignore anything Catholic, and by extension, religious since that was the only game in town.
[*A particular story my dad tells, that still pisses him off to this day, is how the local priest would pull up to their house in his brand new Lincoln Continental demanding his tithe, which my grandparents felt obligated to give him even though they didn’ t have two nickels to rub together.]
Personally, my earliest religious experiences were always confusing and scary to me. My paternal grandmother had this portrait of Christ that look so fucking creepy to me that I was scared to walk past it. The gothic decor of the Lutheran church I’d gone to a few times as a child made me think of Frankenstein’s laboratory. There was just nothing about religion that filled me with any sort of good will. It was all scare tactics (God will be mad at you) or a general malaise about it as a whole.
Once I started thinking for myself, somewhere in my teens, I relized that all the stories I’d been told about religion (at least the prominent ones my family were involved with) were absolutely ridiculous on the surface. Noah’s ark? Parting the Red Sea? Staffs turned into serpants? Burning bushes that talked? I took it all in and realized what a schuck it all was.
So that was the personal turning of my back, I guess you could say. But still, as I learned more about the world and the world’s religions it occurred to me how arrogant it is of virtually every religion to proclaim truths based on nothing more than myths and faith, to the extent that any other religion is ostensibly ruled out. In my book, that just rules them all out.
Short answer to the OP: What led me to “lose my religion” (although it’s more accurate to state "What led me to not subscribe to a religion in the first place) was my ability to reason.
So, this has been such a gradual thing, with every puzzle piece that clicks into place being hard fought for, that there’s still so much that can trip me up and send me to my unhappy place (IE: being terrified of eternal hellfire that some of know so well) it makes me angry.