The hardest thing I've ever done was probably university.

I've been depressed/suicidal for a long time, but university brought out the worst of it. I became too depressed to eat- and I mean that I just didn't have an appetite. Food was a chore. Textures and tastes were just too much information. A meal consisted of a glass of milk, and one potato was supper. 

Eventually I got extremely sick, continuous running fever, and I just went through a very bad break up - no friends of family were anywhere closer than 8 hours away to help me. If I tried to get out of bed, my body would start to convulse. I was eating a single can of beans a day (75 cal). I remember when I finally kicked that bug, I had trouble getting into the shower, and my legs were probably... about six inches in diameter. 

(When I realized how little I was eating, I became an A&W regular. This probably saved my life LOL)

Later, in a different downward spiral, I had acute exhaustion and was sleeping 16 hours a day (and still managed to pass the year and keep my job!) but it made me put myself on medication (secretly, because my parents didn't support it at the time). Good thing, because later on a student in my class jumped off a bridge and died, and a first year in my program was found hanging in her room after three days of being missing (ripe). 

And yet somehow, I still have mostly good memories of univerity. I think that's no easy feat!