The psyche of the writer

"There's a widely held view that by living an unhealthy lifestyle a writer can remove himself from the profane world and attain a kind of purity that has artistic value. [...]
Basically I agree with the view that writing novels is an unhealthy type of work. When we set off to write a novel, when we use writing to create a story, like it or not a kind of toxin that lies deep down in all humanity rises to the surface. All writers have to come face-to-face with this toxin and, aware of the danger involved, discover a way to deal with it, because otherwise no creative activity in the real sense can take place. [...]
So from the start, artistic activity contains elements that are unhealthy and antisocial. I'll admit this. This is why among writers and other artists there are quite a few whose real lives are decadent or who pretend to be antisocial. I can understand this. Or, rather, I don't necessarily deny this phenomenon. [...]
But those of us hoping to have long careers as professional writers have to develop an autoimmune system of our own that can resist the dangerous (in some cases lethal) toxin that resides within. Do this, and we can more efficiently dispose of even stronger toxins. In other words, we can create even more powerful narratives to deal with these. But you need a great deal of energy to create an immune system and maintain it over over a long period. You have to find that energy somewhere, and where else to find it but in our own basic physical being?
[...]
To deal with something unhealthy, a person needs to be as healthy as possible. That's my motto. In other words, an unhealthy soul requires a healthy body. [...] The healthy and the unhealthy are not necessarily at opposite ends of the spectrum. They don't stand in opposition to each other, but rather complement each other, and in some cases even band together."

Haruki Murakami, What I talk about when I talk about running, Chapter 5.