After so many years, I've learned that being creative is a full-time job with its own daily patterns. That's why writers, for example, like to establish routines for themselves. The most productive ones get started early in the morning, when the world is quiet, the phones aren't ringing, and their minds are rested, alert, and not yet polluted by other people's words.
The Creative Habit: Learn It and Use It for Life (ed. Simon and Schuster, 2003)