It may take you a while to discover your best time (and worst time) or you may already know that but just wish it t'weren't so.
Here's what Little Willie had to say about that in How to Write Your Novel in Nine Weeks:
It doesn’t matter if you are a night owl or an early bird. There’s probably a best time of the day for you when it comes to writing. Some writers discover, much to their horror, that they may be night owls but they do their best writing first thing in the (early!) morning. That means while they’re working on a book they have to get to bed earlier than they like in order to get up earlier than they ever wanted to.
Or it might be because of other demands—family, job, life—some writers can’t get to their manuscripts until late in the evening. That’s when the household is finally quiet and they can have that forty-five minutes or an hour to themselves. As you’re discovering, if you didn’t already know, having a block of quiet and uninterrupted time makes a huge difference in your ability to concentrate and write.
True story: When my own family was pestering me in so many ways and I had very little time to myself to work, I’d crack off a sonnet. There! At least I got something done! (“When, in disgrace with fortune and men’s eyes/I all alone beweep my outcast state” . . . in the loo. Really. “Papa! Papa! I have to . . . ” “Give me a minute, Hamnet!” Yes, the little dear’s name was Hamnet.)
Find your time. Find your place. And keep it sacred.
Just keep writing.