most important thing for a novelist

After focus, the next most important thing for a novelist is, hands down, endurance. If you concentrate on writing three or four hours a day and feel tired after a week of this, you’re not going to be able to write a long work. What’s needed for a writer of fiction—at least one who hopes to write a novel—is the energy to focus every day for half a year, or a year, or two years. You can compare it to breathing. 

Haruki Murakami