I haven't had writer's block as a fiction writer, but when I wrote my dissertation, I had long periods where I wouldn't be able to write. I would procrastinate like crazy. It was a sign, I think, that I just wasn't ready to finish. To be a "grown up."
For fiction, I try to write a little bit every day. Even if it's just a few hundred words, if you write every day, you keep in practice. And if I can't get a little writing out, I research, do a Pinterest folder for the story, or, believe it or not, take a nap. A lucid nap can add a story element better than you realize.