I work and go to school full time while writing so I totally feel your pain.
One things that's worked for me if consistently writing everyday (or most days) and committing to a time I'm going to do that.
Sometimes that means I'm writing during my lunch hour, or I'm waking up earlier to write before work. Other times, it means canceling/saying no plans in order to catch up. I may only write 300-500 words on some days but that's words on the page and that's what matters.
It can be a balancing act that may require adjustments. Which includes some self-care too!
I keep a planner and I give myself a star stick whenever I write 500 words. As you can see, I'm not always successful in writing every day but it's a small reward for myself when I do (and it's nice when those stars add up) and it's also a helpful reminder of "Yo, you haven't' written in almost a week. Let's go."