I’m retired, and a long term humanist. I had no religious training, but my mother taught me to read using mythology books. When my aunt decided I need inculcation she gave me a child’s bible when I was seven. I loved it because it was the source of all sorts of great fairytales.
When I was ten I heard the word, "atheist" and felt it described me. When I was twelve, I got involved in the scientific method and realized the only logical choice based on lack of proof was agnostic, so I switched.
This lasted until my first year of college when my girlfriend who was much brighter than I asked, apropos of nothing, "Do you believe in Santa Claus?"
I said I didn’t, so she went through, Easter Bunny, Tooth Fairy, and a few others. Then she said, "Do you believe in God?"
"You know that I’m an agnostic" I said.
"Do you have any proof that Santa Claus and the others DON’T exist?"
"Of course not."
Then how can you declare that you don’t believe in them? Shouldn’t you be a Tooth Fairy agnostic?"
I didn’t speak to her for a week. Since then I’ve been an atheist.
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I was at a party many years ago, and someone asked, "When did you decide you were an atheist?"
I made the mistake of taking a breath before I answered, because my wife quickly said, "As soon as he realized that if there were a god, it wasn’t him."
She almost became my ex-wife for that one. 
Occam
