Having to step up and not only co-lead a WoW raiding guild during vanilla, but also help to lead raids, while tanking as well as doing the various administrative stuff. Wasn't doing it entirely alone, but it sure felt like it at times. After a few months of that, and giving the finger to the special snowflakes that had initially left us in a lurch, thinking we couldn't do anything without them (we were halfway through Blackwing Lair when they left, and finished it three weeks later), I had to disband the guild. The game wasn't fun, and I was spending more time stressing out over doing all of the things I was only doing because no one else had stepped up. Reformed on a different server though with at least a third of that guild as TBC was launching, and I made sure that I would not be put in such a position again, and the next four years were pretty great.
We lucked out though with a random applicant who was going around helping everyone at the time. He turned out to be not only a great tank, but a fantastic raid leader as well.
