Here is a recent interview with Grossman.
It’s still hard sometimes keeping a connection to the fictional worlds I’m trying to nurse into being — life intrudes a lot. But there’s a true thing people say about writing, which is that some people can’t not do it. They can’t help it. So even when I’m walking around, doing errands, getting the car fixed, taking the cat to the vet and so on I’m thinking through stories and characters and sometimes just individual sentences, turning them over in my head. It never stops. I can’t turn it off.This is similar to other writers' descriptions. They write because they very nearly have to. I wish I had that.