Aside from simply being there and being available, the early morning hours are well suited to writing because of the relatively uncluttered state of the human brain at five or six a.m.
Even by eight o’clock, the cares of the day start creeping in: How will I pay those bills? Got to call the insurance agent. Is it freezing out? Got to salt the walk way for the letter carrier. These are picky details, and each one is important to address, eventually. But the more the day wears on, the more room these cares take up in the brain, leaving less room, less energy for the focussed attention required by fiction writing.
I noticed this the other day when, after four days of very early mornings in a row, I did my writing a little later in the a.m. Like ghostly footsteps on the stairs, the worries of daily life came creeping up on me, stealing my attention momentarily, here and there.
I still managed to re-focus and get my work done, but there was an extra battle to fight along the way.
God bless the early morning.