The most annoying thing in the world? Witnessing an argument and knowing exactly what needs to be said, and what needs to be asked, to resolve it, but those involved being so engrossed in it that none of them will listen to hear what they need to hear.
No; that’s not right; the most annoying thing in the world: when one of the people involved in said argument is so self-righteous about what they’re trying to say that instead of listening to what the other people are actually asking, they keep re-iterating their point, which isn’t actually the answer to the question being asked.
I’m still not sure that’s quite it… perhaps this is it:
Losing faith in something you love.