Okay, I don't know how to do links, but check out the above link for more information on "Reveal".
So what is it? Well, it's a pretty amazing study on what actually helps people grow spiritually. Rather than a bunch of pastors saying "here's what I think helps people grow" - the study is done of actual "non-pastors!" who want to be fully devoted to Jesus Christ! So, it's pretty revealing, in a way, of what helps people grow and when. When? Well, sometimes one thing helps you grow, and other times its a different thing. Let me cut to the chase.
Mature Christians get very unhappy with their church and their personal "growth rate" UNLESS they are actively serving the under-resourced. Of course, that's not the whole story - but it's a big piece of the story, that's for sure.
So, you wanna grow spiritually? Serve someone less fortunate - that's a great start!