I hear people say they write every day, they make a habit of it. I always assumed this meant writing on topic, on whatever your projects are.
Really, it just means write something. Even complaining about yourself or writing a description of a bird. The point is to be practicing, to stay in training, to keep your sword-mind sharp, as Tyrion once explained when it comes to reading (the other daily practice).
Often, nothing for your deadlines will come. For some people it comes in little slices that will add up over time and be edited into perfection, for others (like me) it’s all at once in a deluge of words that need to be typed down before they flow away down the gutter.
Writing every day gives you the chance to start, and to get closer to finishing. You can rely on the muse to inspire your writing, but the muse needs to know when and where to find you.
And, even if it’s just journaling, you’ll help your psychology, and create a log of what happened that day – filling the tanks for when the muse does come. Think of artists doodling and doing “studies” all the time. So many good books are just worked over diary entries and collections of anecdotes.
(The above is pulled – like those little slices – from writing advice I’ve read elsewhere [esp. the muse metaphor]. Related writing tip: don’t worry about hyperlinks if you don’t have the time: click publish and move on.)