Sometimes, I can feel utterly lonely standing in the middle of a crowded room.

It usually happens during a bout of depression, but there have been times I felt it when manic because I just KNEW nobody would ever understand what was running through my mind. Bipolar really is a lonely disease, particularly when you live with people who have no idea what it's like to live inside your head. I have a great support system as well as a number of online friends with the disorder, but not a single person IRL really "gets it".