There you are sitting at your typewriter, keyboard, keypad, or other input device staring at a blank page or at a blank area under something you've written and you can't get the next word out. This is not something that just happens to people who write for a living, or who hope to do that. It happens to everyone all the time.
There are many circumstances where we just can't find the words to express our feelings or our ideas. For me the most egregious example of this is writing a note on a sympathy card for someone who has just had a person close to them pass away. I have to say something but what can I possibly say?
I suppose we can put writer's block into two circumstances. With one we know what we want to say but can't find the words. The other happens when we draw a total blank; something has to go on the page and we have no clue. There are probably other circumstances we could call writer's block but those two probably deal with most cases.
Of course, this all just gets worse when a schedule gets added to it. The sympathy card has to go out in a timely manner. The person who assigned the essay did so with a due date. The boss wants your report at five o'clock today!
I think writer's block is a disease that has no cure, but there may be treatments for it. Let me entertain some ideas as to what can be done to overcome this uncomfortable situation. I don't know about you but I find writer's block to be extremely uncomfortable, debilitating and disconcerting, and those feelings exacerbate the problem.
Here's an aphorism for you, though I advise you to question these things instead of making them rules. 'Writing is rewriting.' This works well when the deadline for what you are writing is sufficiently in your future and you have time to rewrite. Sitting down to the blank page when the professor/lecturer expects the essay on their desk or in their in box no later than 8 a.m. tomorrow is never a good situation to be in. Hint: start earlier. "That's easy for him to say."
Assuming you have the luxury of time to rewrite then you can look at everything you have to write as a first draft. With that in mind it doesn't matter what you put on the page because you will be coming back to have a second (or third or fourth or fifth) look at it and very possibly change it.
The creative process, when done well, involves a great deal of rejection. Naming characters comes to mind as an example of this. With a fictional narrative you might start with, 'What will I name my protagonist?' To which you may answer, 'Percy Wrinkles.' And you might follow that immediately with, 'No, I don't like that.' You will hold that name in your memory, because you haven't completely rejected it, while you go trying to think of something else. Meantime, nothing goes on the page and you can imagine your publisher, teacher, boss standing behind you, looking at your blank page and tapping their foot.
Here's what to do. Write down, 'Possible protagonist names' and under that write, 'Percy Wrinkles.' Oh, look! You are no longer staring at a blank page. Additionally, you now have something to show for your time and you can prove that you are at least working on what you are attempting to write.
Essentially the thing to do is ignore all your inhibitions for writing things down and just put the words on the page. In other words instead of telling yourself, 'No, that doesn't fit there,' 'No, I don't like that,' 'No, that goes in the conclusion, not the introduction,' tell yourself, 'No, but I'm putting it on the page anyway.' At the very worst, doing that will get you moving and besides, you will come back later to rewrite everything, unless, of course, it's due before 8 a.m. this morning. Even then at least you'll have something to submit instead of nothing.
That takes care of knowing what you want to write but not having words. What about not having anything at all? In that case, you need inspiration. Do you have a muse? Most people don't so I expect the answer to that rhetorical question is 'no.' However you may know someone who will be interested in hearing your plight. "Hi, I need to write something and I have no clue as to what to write." 'Click Bzzzz.' Sorry, but it happens. Hopefully your friend will be a bit more sympathetic than that.
Chances are that if you are sitting staring at a blank page that you have some idea about what you want to write, even if that idea is only that you want to write something. What you need to do is go and look at things and think about how you can use them.
If this is a situation that recurs often you can set yourself up so that you have the inspiration at hand to help you through it. The way you do that is to collect notes and images. Guillermo del Toro keeps notebooks on his projects. He draws pictures in them and writes ideas. Stanley Kubrick used file cards that he kept in little boxes. On the internet there is a web site called Pinterest. You can sign onto that and then post images with notes on them.
If you have some specific idea about what you want to write you can collect specific ideas and images. If you don't have something specific in mind then just collect images and write things down as they occur to you. When you find yourself staring at a blank page with no clue, at least you will have something you have prepared that you can go and look at from which you can take inspiration.
There. I've touched on a few things about writer's block and how to deal with it. This is in no way the final say on the matter. Hopefully it will give you some ideas that will help you when writer's block is your problem.