I'm Scawed!

You can't tell me that there isn't a bossevent you fear... i think there is this fight everyone dreads that he is going to fuck things up for his raid.
A fight you'd rather miss but often can't as your guild/raid needs you.

Mine was Leotheras the Blind for quite a while; This boss spawns inner demons on a few random people throughout the figth and you will have to kill yours (others can't help) before the time runs out.
If you can't kill it you will get mindcontrolled and the raid doesn't just lose a player, they gain an enemy. When we just started this boss the Hunters still had a pretty big deadzone and as pets didn't get the aggro you would need to kite this demon.
Kiting takes time and as a Beastmaster my Arcane shot wasn't as powerfull as of a Marksman hunter so often it was a close call. After some reading up i found out i could use the pet as extra damage dealer (and for one stun to keep it at range) without still getting MC'd (as was the deal before when the pet got the killing blow).
This made it alot easier.
When they removed most of our deadzone shortly after it became even more trivial, i had nothing to fear anymore. But when we just started Leo i'd would get a near heartattack when i saw this demon comming at me.

Depending on your class people seem to be afraid of different fights. At Leo it seemed to be Hunters (at first), Warriors and Locks (who needed the time for dots to tick, probably affliction locks mostly).
In the Black Temple loads of people fear Teron Gorefiend where random people get control over a spirit which needs to kill at least 4 adds before those wipe the raid. Some don't have too much problem with this but those who are a bit less focused or slower with their reactions do.

Overcomming this fear is your own little victory and is best done by actually beating that event you fear so much. Once you've managed to beat it you will be more confident next time, but when it beats you.. next time will be even harder.
State of mind is the key here i suppose.
I remember myself shouting "Take thát Bitch!!" when i kicked my demons butt for the first time, you might imagen how relieved i was after that.
There are probably more examples of certain classes clashing with certain events but i'll leave it to this for now (as i can't think of any at the moment anyway).
Good luck fighting your own fears out there, in virtual or real world ;)