I don't believe in writer's block in the traditional sense. If you can't write, you probably have nothing to say, so you should go find something to say.
But if you feel like you do have something to say and, for some reason, the words and the work aren't flowing, shake things up: do things differently than you normally do them.
If you normally write on a computer, try writing by hand or on a typewriter. If you usually write at home, go to a coffee shop or even a park.
If you use a pen, write with crayons. If you write on paper, write on a napkin or the back of an envelope.
Haruki Murakami, when he was stuck writing his first novel, started writing it in English on a typewriter instead of longhand in Japanese. Writing in English, his brain avoided the "system overload" that accompanied writing in Japanese.
It also led me to the realization that I could express my thoughts and feelings with a limited set of words and grammatical structures, as long as I combined them effectively and linked them together in a skillful manner. Ultimately, I learned that there was no need for a lot of difficult words – I didn't have to try to impress people with beautiful turns of phrases.
Joan Baez, when she feels stuck, writes backwards or with her non-dominant hand.
Somewhere in my teenage years, probably out of boredom, I taught myself how to write backwards, starting with EINAOJ ZEAB, my new name. I worked my way through the Greek alphabet: AHPLA ATEB, AMMAG, ATLED, and so on. I still write backwards as a form of therapy when I need to get to the root of a blockage or calm the buzzing heat of a panic attack. It's as though the appropriate wires cross my brain when I write backwards, which allows information otherwise unavailable to surface.
Later, I began drawing with my left hand instead of my right. Like writing backwards, using my non-dominant hand opened a different compartment in my brain. I discovered the results were less restrained and more fluid, and therefore more interesting to me. >
If you're feeling stuck, shake things up. Do things differently. You may be surprised by what comes out on the other side.