Why do some people pretend to be spiritual and then they come out suddenly and say, "Oh, I was never a christian" etc. Is it because they've seen something where they've stumbled, or could it be because they never had God's spirit with them?

In the more humanistic-psychological way, if that makes sense lol, why would anyone pretend to be a christian or spiritual (looking at it from that person's point of view). I'm talking about those who are adults and who are independent so there would really be no need to pretend.

Also, how do people lose zeal? And how do they gain it to begin with to even want to be involved? :confused:

Yes I believe some lose zeal. Some get into it believing it is what they want but then realize they don't.
Then too you have the people who are into the New Age type stuff that claim being spiritual but not necessarily Christian

You're assuming that being spiritual and being christian are the same thing. They aren't always. Believers in other religions can be spiritual, as can those who claim no religion.

For all intents and purposes, I have no religion. There are no organized religions that I agree with and believe in. however, I still see myself as spiritual.

I'm spiritual and believe in spiritual things and interested. I'm a medium,but I'm not religious at all.

I am a very spiritual person, christianity has nothing to do with my belief! I find the closest religious form for me is budhism.

I'm also a very spiritual person, but not a christian.