Watching a whole cluster of friends, and my own mother, die over quite a short space of time convinced me that purely materialist 'explanations' for our mysterious human existence simply won't do - on an intellectual level.
I am shy to admit that I have followed the advice given all those years ago by a wise archbishop to a bewildered young man: that moments of unbelief 'don't matter,' that if you return to a practice of the faith, faith will return.
When Christians start thinking about Jesus, things start breaking down, they lose their faith. It's perfectly possible to go to church every Sunday and not ask any questions, just because you like it as a way of life. They fear that if they ask questions they'll lose their Christ, the very linchpin of their religion.