Throughout my time playing Civilization (from 2 to 5), I've only begun to ragequit during BNW. The only thing that sparks it is combat. I've often built up a more than adequate military to siege an enemy capital, worked it down to 0 health, and always had my melee units wiped out by the city + a CB/Crossbowman. I can't ever seem to just CAPTURE the city - after that fails, and I try to bring more melee units, all my siege and ranged are destroyed (1-2 per turn) and I realize I've just wasted 30+ turns focusing on siegeing an impenetrable city.
This has happened thrice:
-Siegeing Beijing, London, and Onondaga