I read this book by William Lobdell, Losing My Religion, and it was a life-changer. I hated it, loved it, was completely ripped up inside while reading it and afterwards.
A few quotes:
...[it] was the first tangible sign that I was losing my faith. But the thought was so scary, so unwanted and so profound that it would be a long time before I actually admitted it, even to myself.
My long honeymoon with Christianity had ended. As soon as I'd beat back one doubt, two more would pop up.
Spiritual suicide infers that people make a conscious decision to abandon their faith. Yet it simply isn't a matter of will. Many want desperately to believe, but just can't. They may feel tortured that their faith has evaporated, but they can't will it back into existence. If an autopsy could be done on their spiritual life, the cause of death wouldn't be murder or suicide. It would be natural causes - the organic death of a belief system that collapsed under the weight of experience and reason.