For German speakers, an interesting article in the Neue Zürcher Zeitung by Terezia Mora, "Die Dichterin in ihrer Zeit."
Mora begins by saying that when she worked on a novel for four years, almost none of what she wrote during the first three years actually ended up in the final book!
She also mentions reading Ulysses when she needs perspective on her work, because a) it is hilariously funny and b) she enjoys the freedom and courage and poetic power of the book. Joyce as an antidote to one's own limitations?
Finally, she also says that before she wrote her first story (which ended up in her first book), she was not sure whether she would ever write a successful sentence. But before she wrote her second book, she already had a definite and rather rigorous image of a) what literature should be like, b) what, within literature, her own literature should and could be like, and c) what, correspondingly, her second book should be, both as a whole and in the details.
That says a lot about how writers have "systems" even if they do not want to define them, but also about how such systems derive from one's own experience of writing. Writers best define their own worlds through the work they produce, not through their theoretical statements about that work.