I've been doing a lot of writing lately, and found an interesting pattern developing: I write poetry in the morning and prose at night, often late at night. Trying to reverse the pattern doesn't work at all.
It seems to me that poetry is so closely related to a dream state (Rilke would agree) that when you first wake up, the subconscious is more accessible -- the area of the mind that understands symbolically rather than logically.
Later in the day, at night, after a day filled with people and conversations, the realm of character is vivid, and yet a little fatigue creeping in brings you back closer to the dream state again, but this time from a different angle. Less oriented to deeper layers of the self, and more to the superficial layers where social intercourse make their impressions.
Thus, fiction is best written at night, and poetry in the morning, the earlier the better.
Might just be me, but other writers have reported a link to the dream state and writing:
Maya Angelou on dreaming and writing: “I do believe dreams have a function,” says Angelou in Writers Dreaming. “I don’t see anything that has no function, not anything that has been created. I may not understand its function or be able to even use it, make it utile, but I believe it has a reason. The brain is so strange and wondrous in its mystery. I think it creates a number of things for itself – it creates launching pads and resting places – and it lets steam off and it reworks itself.”
Amy Tan on dreaming and writing: “The kind of imagination I use in writing, when I try to lose control of consciousness, works very much like dreams,” says Tan in Writers Dreaming. “The subconscious takes over and it’s fun. I discover things I could never pull up if I were really trying to. When I get into a dream world I can create fiction by going down surprising pathways.”
I found these quotes on a wonderful site for writers, The Adventurous Writer. "So much depends upon a red wheelbarrow."