I think my experiences of loss of faith have been a necessary part of my journey, too. I can't really articulate what made me convert or de-convert each time, though - it's always happened somewhere in the depths of my subconscious, and next thing I'd know, I'd be standing up saying the Creed and meaning it or telling a friend "I don't define as Christian any more", as the case might be. It would only be in saying it that I'd become aware of the change myself.

As for what constitutes "working" in this context - for me, it's some combination of "gives me a language in which I can express my experiences without too much distortion" and "stops Them driving me crazy by poking me to let me know I'm Doing It Wrong" ;-)