Well, I was a big cheese hound, and tried to go vegan a couple of years ago. Surprizingly, it was easy.... aside from one thing: eggs! I learnt that while cheese wasn't as big as a problem as I thought, eggs were starting to prey on my mind. In the end I caved when I was given scrambled eggs by mistake, and I went back to my vegetarian ways.
One good thing did come out of it though: ever since that vegan attempt I've considerably cut down on my cheese intake and really don't miss it. Eggs? Love 'em!