When writing becomes a habit and a necessity, the writer need never give a thought to discipline, because writing is a pleasure. Then friends and relatives will say, "Ah, what discipline!" on seeing the writer at work, not realizing that it would take more discipline than they dream of for him to spend the next few hours in their company.
Exactly. I've always felt that the praise was unearned when people tell me they admire my discipline in finishing novels. After all, I only do it because I really want to, not for reasons of morality or health or civic duty. *shrug*
(She does add, and I do agree with this too: "After a good day's work, when one is feeling rather godlike, it is a different matter; a writer looks on the human race with a new joy, and feels like saying even to the Fuller Brush man, 'Come in! Got time to sit down for a few minutes?'" Not that we have Fuller Brush men anymore.)