It's a bit strange, but I often feel very sick if I've been concentrating on novel creation for extended periods. Just a nausea, and it's pretty irritating and immediately kills your ability to concentrate. It's not quite so bad when writing but I get it a lot when I'm brainstorming or doing concept art or anything inherently creative. I used to play video games quite a lot when I was younger, for hours on end and I never had/have any problems doing that. When trying to work on my novel though I get ill after an hour or two. Strangely it's usually not headaches like I said, it's almost always nausea. thoughts?