I read the Bible.
Ha, no, kidding. That's part of it though. I always had trouble believing, even when I was a small child. When my parents would take me to church, I always thought it was just something they did for fun, like going to a play. I had no idea they genuinely believed. I had panic disorder and would stay up all night worrying about death, and it would frustrate me when people would talk about Heaven to make me feel better because I had no idea why they were still telling their stories when I wanted a real answer, not entertainment.
I'm not denying that there's some sort of supreme life form out there beyond our comprehension. It's possible. I just have trouble, a lot of trouble, with established religion and how the concept of an afterlife tends to belittle the value of life while it's still alive.