Depression is something that doesn't just go away. It's just... there and you deal with it. It's like... malaria or something. Maybe it won't be cured, but you've got to take the medication you're prescribed, and you stay out of situations that are going to trigger it.
I've never really been nervous about any concerts. I enjoy it so much. All that matters is getting the songs played well, trying to get them to sound as close to the record live, which isn't easy, because my music is quite complicated to play.
Bipolar disorder, manic depression, depression, black dog, whatever you want to call it, is inherent in our society. It's a product of stress and in my case over-work.