At 35 I'm definitely starting to feel more like a grown-up than I ever have. There's nothing in my life that is childish or whimsical. Having fun is fantastic and I never want to lose a sense of that - and also I think you have to have that to put into your work or else it's going to feel stiff.
When you're young you're always wondering when you're actually going to feel like a grownup. And I think you probably fear it in a sense too. There's a danger to feeling like an adult... like this whimsical kid in you is going to die or something. And then all of a sudden one day you kind of feel like an adult and it's really nice.
I write for no other purpose than to add to the beauty that now belongs to me. I write a book for no other reason than to add three or four hundred acres to my magnificent estate.