I believe in the power of myth. But i'm like Campbell itself. I play to believe each religion, but in theirs metaphoric meanings (Like, for example, a pedagogic way of insert a person in a given reality of a society, teaching Its rules), never in It's literal way: God Like a entity that really exists, Apple tree, heaven&hell, Mjolnir, Shiva, Ashanti: things and beings like that are for me just metaphoric constructions to prove a point. However, religions never were "built" rationally and here I must quote a guy that represents well all of this, Joseph Campbell:
"God is a metaphor for that which transcends all levels of intellectual thought. It's as simple as that."
I believe, then, in spirituality as something intrinsic to mankind. But I myself don't practice.
For whose whants to begin understand psychological, sociological, philosophical and historical meaning of Myth/Religion/God, start here: (1/6 volumes of interview, but the guy has a lot of books written). Dont worry! He speaks to the lay and to the experts.
Also, read Freud (totem&tabu), Rudolf Otto, Jostein Gaarder, Mircea Eliade, if deepen understanding is needed. To this theme, ignore Marx, he didnt knew what religion was about.