Showing up here, where there are tens of thousands (well, a few dozen) potential converts, and most believers seem to say to themselves "Wowsers, this should be easy!" Apparently it isn't.
I can't speak from experience because what little belief I had was long, long ago. But I've always sort of assumed that those who really believe do so without giving the subject much thought, and they have no idea how unset in stone their own justifications are. Let alone anything about how inadequate their self-knowledge about their own religious mind is.
Mostly because they've never really thought about it, and hence they soon find themselves tripping over their own words as they try to put them in a form that both they and we can understand. Which apparently is not possible. So they hope that we atheists will say something that qualifies as useful feedback, of the positive variety, of course. We keep forgetting to do that.
But since they are mired in their own misplaced certainty, there isn't much else they can do. Except leave in frustration. Which most end up doing.