It's best to have a set time to write every day. Not the perfect time - because that never happens - but a scheduled, and logical, time. For a night owl like me, trying to write at five in the morning would be a waste of time.
I like the way the creative process is described on the site Brain Pickings:
"Because creativity, after all, is a combinatorial force. It’s our ability to tap into the mental pool of resources — ideas, insights, knowledge, inspiration — that we’ve accumulated over the years just by being present and alive and awake to the world, and to combine them in extraordinary new ways. In order for us to truly create and contribute to culture, we have to be able to connect countless dots, to cross-pollinate ideas from a wealth of disciplines, to combine and recombine these ideas and build new ideas — like LEGOs. The more of these building blocks we have, and the more diverse their shapes and colors, the more interesting our creations will become."In the post The Daily Routines of Famous Writers, there are some great routines by some very well-known, successful writers. You have to admire their persistence...and, for most, the lack of modern conveniences that we take for granted.
The point is, do whatever works for you, but by all means, do it. And try to do it daily. The writers in this article produced some beautiful writing over their lifetimes. Some are still with us, some are long gone. But, isn't that one of the coolest things about writing? Once it's in print, the words live on with us forever.