Write 500 words on any topic you like. Now remove 250 of them without changing the essence of your post.
I’ve past a great deal of my professional life writing texts and adjusting them later to a specific length to fill a column, or a page in my newspaper. So I’m used to use mental scissors to remove words without changing the meaning of the article. It’s easier when you apply the rule to put the essence of your story at the beginning.
I had a boss very indecisive. I remember one evening, after a concert, when he told me that my story would go in half a page with a picture. So I wrote a long reportage with all sort of details about a cultural event, including a little interview with an orchestra conductor. Later, he told me there was no space and my story would go in one column , with a small picture of the conductor. So I had to cut my text to the essence. Finally he came back and told me he had found two columns free for my story, so I had to rewrite it and made it long enough. For me it was easier to cut the text than to rewrite the story once deleted. I had to remember all the details, search again in my notes and so on. It was a very long night.