I'll tell you what works for me: "little but often" and "create a habit, and then the habit creates you".
I think it is Picasso who said "when inspiration comes, let it find you working".
You create a space for that thing in your life, a space for that everyday, and you see it as a happy moment, never as a chore. It doesn't have to be much, in your busiest moments you can reduce it to half an hour a day; but it has to be every-single-day. Use checklists or beginning rituals to help you "tune in" or enter the "zone" quickly. Create a structure that helps you slide into it, and, just like you use your creativity for your writing, improve that structure with new ideas as they come.
Some of those days go well and others go bad. Some of them you will just stare at the wall daydreaming, and others will be very productive. Some of them will be little more than a "filling in the box", but they have their value too, as a symbolic act, and also for the way in which they train your brain. "Discipline is remembering what we love", said Einstein.
The force of habit is powerful, and once you've done it for a while, you'll see that once you skip one of those days, you'll miss it, and perhaps will go "you know what? I planned to skip my stuff today because I thought I would be too crushed, but I've suddenly found this half an hour here and..." We're wired for habit...