Get up and pick up a pen. A physical pen. A physical piece of paper. Sit on your bed and not your desk. Sit outside. Move. You don't have to write on a computer and you don't need to write at a table.

If you can write a good argumentative essay, you can write good fiction. Fiction is the same thing, except you can make all the points up as you go. The same logic applies, however. What are you trying to argue and how will you argue it?

Anyone who tries to tell you that creativity is essentially magic that some people are born with are not worth listening to. Creativity is problem-solving. Anyone can do that. It's just hard sometimes.

Do you need a 500k book or do you just want to tell people you wrote 500k words? You do realise you have to edit that, or pay someone to edit that, right? Everyone will thank you for writing less, but the real fun is writing more with less. That's how you write well.