When one is a professional artist, one must paint whether one feels like painting or even if one is not sure WHAT to paint.
It's that way with writing, too. I'm not a professional writer, although I have sold some of my writing in years past. But as with art, I'm driven (a little, in this case) to write, too.
But ideas for art come quite easily. As a landscape painter, I only have to go outside into a beautiful area (and I live in such an area) -- then I'm inspired, which gives me the energy to "go to the studio and make stuff." (I have a watchface that says that!)
It's never been that simple with writing. Once I know what to write about, I'm fine. But thinking of what to write about -- that's always been a problem for me. I always hated it when some grade-school teacher gave us a carte blanche writing assignment. Of course, we had to fulfill certain criteria, but beyond that, we had to come up with our own ideas for a subject. Sometimes I didn't think of an idea until it was almost too late to write about it.
In his book, "The Courage to Create," author Rollo May made a comment about artists "confronting their art." Confronting -- that's an apt way to describe it. Art (which includes writing, in this case) can be a leisurely pasttime, but for many of us artzy types, art is work. Maybe that's why they call this stuff "artwork." And writers "work" on their manuscripts.
Funny, tho' -- musicians play instruments! Go figure.