I never chose to believe in god. I was taught that there was a god, and I was taught that we could contact or commune with god through prayer, and I interpreted every numinous experience and every instance of insight in the light of that communion.
As my Christianity matured, and as I better internalized Orthodox mystical theology, I came to understand that what I believed about god was metaphorical and provisional, and did not express any objective reality about god. It was, of course, my choice to be Orthodox and my choice to immerse myself in Orthodox teachings, but this deepening understand also didn't feel like a choice, but more like a dawning realization.
I chose to leave the Church for moral reasons having nothing to do with its dogma or mystical theology. (However, some things that are not matters of dogma in the Orthodox Church are matters of dogma in the Western churches, so I could not have said that if I had been leaving, say, Catholicism.) Leaving the Church was a painful and traumatic decision, but it was also a liberating decision. I came to believe that since the way I understood god was metaphorical and provisional, there was no particular need to hold to that particular metaphor. Actually, I had begun to think so before I left the Church, but before I left I also had no particular reason to go beyond that metaphor. Again, there was choice involved, but my evolving way of understanding things didn't feel like a choice.
As I considered other possible outlets for my religious impulse, I didn't see any point in affiliating with another dogmatic religion or learning a new metaphor. Also, I had come to see myself as a member of a people. A religion is not just an intellectual proposition, but a community, and the community I belonged to was the one the Greeks call the Romaioi and the Arabs call the Rum Urthudux. Having made myself an exile from my community, I could choose, as it were, another place of residence and another nationality, but I was no longer at a point in my life when I could choose a new identity. A boy or a young man can leave home and become a Frenchman; a man in middle age can go to live in France and even take up French nationality, but he can't really become a Frenchman.
In my unaffiliated state, I had the opportunity to observe what I really believed without any pressure to accept any particular framework of belief, and I really that the god metaphor was no longer useful, and no longer had any meaning to me. Once apart from my community, I realized I didn't believe in god.
That's a simplified version of what happened, but everything that happened in my own life leads me to think that while we may not choose to believe or not to believe, we do make choices that make any belief or disbelief possible. We choose to be open, to inquire, to continue our pilgrimage, or we choose to be closed, to accept, to sojourn where we find ourselves. Those kinds of choices so influence our worldview and the way we think about god, that our beliefs about god don't seem like choices at all. But I suppose that ultimately they do or at least can result from our other choices.
As an aside, I should note that while my particular pilgrimage has taken me through several religious traditions, there are people who make just as far-ranging a pilgrimage but do it within a single tradition, or who -- early on -- find a tradition that continues to allow them the range they need. I don't think that's necessarily any more unhealthy, psychologically, than my own experience. I do think it's unhealthy to stop changing and growing, and I do think that in that respect, religious dogma is unhealthy and even destructive. My grandmother found in her own back yard the kind of wonder and depth of experience that I can only find by traveling. Both are good. It's when you say to your own that if they leave the back yard they are no longer of you, that problems and conflicts arise.