For the most part, I don't believe in writing muses - I believe that when you sit down and get to work, that opens up doors for ideas and inspiration. You've got to be listening if you want to hear them. However, I very much believe that there are certain things we can each do to get ourselves in the writing zone and prepare ourselves to do that work.
The tricky part, though, is that those things are going to be different for each person, and sometimes it's a matter of experimentation to discover what they are. I'll share some of mine with you, and I'd love it if you shared yours in the comments. This will help us all brainstorm new things to try.
1. I absolutely must be wearing sweats, pajama bottoms, or knit pants when I sit down to work. I've found that if I'm wearing jeans (too stiff) or a skirt (my legs stick together), I can't concentrate. I need the joy and peace and harmony of stretchy cotton. And in order to illustrate this concept to its greatest potential, I present this to you.
2. There are certain times of day that are better for me to do certain tasks. I check my emails and do my administrative stuff in the late morning/early afternoon. I can edit in the late afternoon/evening, and then my best writing time happens starting at around nine p.m. and goes until around 2:00 a.m. That's just the weird way my body is wired. If I wake up and try to write first thing, I'll sit here and stare at the computer for an hour, which is a total waste of time. I've learned when my brain is best at each thing, and I stick to that schedule.
3. I must have water sitting next to me. Writing is thirsty work, y'all! It also helps keep me more alert, and the need to use the bathroom regularly gets me up and moving around at least a little bit once in a while. When I run out of water, my productivity immediately goes down. My family knows me well enough that sometimes when I call out to them, they'll come find me with a cup of water already in hand because they've anticipated what I'm going to ask them for. (Yes, I do use my family like indentured servants. It's good for them. Puts hair on their chests.)
4. Another thing I have found is that I write better when I have a constant input of stories, either books or movies. I don't steal ideas from these sources, but they open up the doors of my imagination and allow my brain to create more freely. Any time I get stuck on a book, I'll take a few hours and watch shows or read, and I'll soon find that I'm unlocked again. I actually prefer to watch a show to reading during those times, though, because I need to engage different parts of my brain than I've been using.
Whenever you have a good writing day, take a look at what your routine was and see if you can identify some key points to what made it successful. I used to think I could only write in quiet ... yeah, well, then I had kids and it was either learn how to write with chaos or never write again. We adapt and adjust. But if there are certain things that seem to help you, pay attention to those and make the most of the writing time you have.