You know the phrase ignorance is bliss? I want to tell someone — but nicely — that the reason they're not worried about something is that they just don't know the details.
Something like, I hate to break it to you, but you're in a state of ______. But not denial — that's way too active. Same with sticking your head in the sand. A fool's paradise, except I don't want to call anyone a fool. I thought of "you're just not looking behind the curtain", which I guess would work, but I don't think is a common expression.
I know there must be a phrase for this, but I can't think of it.