Merriam-Webster defines writer's block as "a psychological inhibition preventing a writer from proceeding with a piece."
In other words, it's a kind of creative
I've never bought into the concept of writer's block. It seems like something that was invented by a meek Hollywood screenwriter, glamorized in film noir with boozing, womanizing scribes played by the handsome actor. It seems to me that a writer writes. The urge is almost pathological. The goal is not to be famous, or rich. Writers write because they have to. The goal is to get those words out.
Ever heard of hypergraphia? It's a psychological condition in which the sufferer has an uncontrollable urge to write. It doesn't even have to be coherent sentences or words: it can be complete gibberish (see: James Joyce's Finnegan's Wake).
Hypergraphia is a real condition;
writer's block is fictional.
The first step to cure writer's block is to admit this to yourself. Unlike the alcoholism you might truly be afflicted with (being a writer, and all), the first step is to admit you don't have a problem.
That kid in The Matrix, telling Neo how to bend the spoon? "The trick is not to bend the spoon, that's impossible. The trick is to realize there is no spoon." (To paraphrase.) It's the same with writer's block. If you don't believe in it, it won't exist.
I know this might sound smug or glib, but I really believe it to be true. I've never suffered a moment of writer's block. I may have hemmed and hawed about what to write next, and I may have stopped writing a novel for two years before picking it up again, and I may also have made a hundred or more false starts only to give up after a couple of pages, but I never stopped writing.
You can spend hours procrastinating, days even. You can surf the internet, or research, or masturbate, or go for a walk, or play with your kids, or take up heroin, or read countless manuals on how to get over writer's block, but the key is when you're finished wallowing in your own self-pity: write.
A poem, a new book, a short story, a monologue, article, review, screenplay, a letter to your grandmother in Kalamazoo. Literally write anything and you've purged the invisible demon Writer's Block.
If you're shouting "But I really do have writer's block!" at the screen, think about how you feel when you're sitting in front of that blinking cursor (or typewriter carriage, if you've taken Hollywood's badboy writer trope a little too seriously). Think about what's going through your mind while you're there.
"I know I can't, I know I can't..."
Is it something like that?
Or "I've got a deadline, I'll never get this finished in time"?
Or "Maybe I'm not really a writer"?
Who knows? Maybe you're not. Would it be that awful to quit? (If the answer is "yes," you have passed the first of Three Tests.)
If you've got a deadline, sit down in front of the computer comforted by the knowledge that you may write a whole stack of shit, but at least you'll be writing.
If it's "I know I can't," try telling yourself why you can't. If your first thought is "I won't measure up," write more, read more, and someday you will. But the point is, you don't need to measure up.
You just need to write.
Don't worry about a daily word count. That sort of obsessive structure is limiting, and can actually worsen your fears and doubts, creating this imaginary boogeyman called "writer's block."
Write. Edit. Delete whole pages. Start over. Finish something and move on to the next. Like a shark moving forward just to stay alive*, you should always be moving from one project to the next. Slay that mythical beast. And when you finish that book or that screenplay or that short story or that letter to Nana in Kalamazoo, congratulate yourself in the comments section below.