I haven't really changed my mind about anything major, but in my defence, I only joined this site recently. The only thing I can think of is my conception of prayer. I posted a meme asking people their thoughts on the efficacy of prayer, thinking that most people saw it essentially as asking God for a favour. But for the most part, the comments didn't bear that out. That's a very small sample size, of course, and I'm still aware that stuff like faith healing exists, but from now on, I'll be less likely to assume that when someone says they'll pray for something, they think that will be enough. Now, I'll consider the possibility that they're like the people who answered the meme.