I have major problems with the idea of a "birth religion", but as far as religious influences growing up, I didn't really have religion pushed on me much growing up, but what influences I did have were Christian, primarily Baptist.
When I was little, we had a book of children's Bible stories that I would read occasionally, but it was never forced on me. I don't recall my Mom going to church until I was a tween, and while I was never told to come with her, I was welcome to come and did go occasionally. I found it pretty boring, and the kid's program awkward mainly because I didn't know the other people.
My main religious influence probably came from my grandmother. When I was little, I'd stay over at her house a fair bit, and if it ended up that I was there on a Sunday morning, she'd suggest going to church, but she wouldn't push it on me - if I was excited to ride the subway all day (when I was 8 or so, that was one of my favourite things to do. I was a weird kid, I know.
), she'd skip.church and take me to do what I wanted.
I'm not sure that I was ever so into religion that I had to "leave" per se. I remember when I was 13 or so, I found out that one of my classmates was VERY Christian - very devout, only listened to Christian music, all that. At the time, I was rather shocked: I simply couldn't wrap my head around the idea that anyone could take religion that seriously.
I don't know if this is what you're after, but looking back, I think that one of the big influences on my views on religion happened when I was around that same age... like grade 6 to grade 7 or 8. I got really into Greek mythology. I loved reading the stories - I had a kid's version of the Odyssey, as well as an "encyclopedia" of Greek mythology, and I read them over and over. The way they were presented to me as a kid, though, wasn't as literal fact; it was more as what ancient people believed, and something that can communicate meaningful messages through a non-literal interpretation, as well as being just fun, exciting stories.
Once I had this mindset in place about the Greek myths, I think I recognized the similarities in "storytelling feeling" (that's probably not the right term, but it's as close as I can get right now) between those myths and the Nativity story I'd get at our Christmas assemblies every year and the other Gospel stories I would get at my occasional visits to church, so I approached those stories in the same way: as vehicles to communicate meaning, but not as something that anyone would be expected to take literally. When I later found out that people do take these stories literally, I was very surprised.