Short stories are harder and easier than most other types of writing. It is difficult to fit a whole story in so little space. They tend to be dense because every piece of information is relevant to the story. The characters have to develop and change while the ending usually has some sort of twist for the reader. However, short stories can be the easiest things in the world when the ideas hits like a thunderbolt and sizzles down through the fingers. That moment is one of those great moments in a writer’s life.
I believe that a short story should be written in one sitting. Any other form of writing can take longer, but a short story should be done quickly. I have pieces of short stories sitting there waiting for me to get back to them. None of them flow quite as they did when I sat down to write them the first time. Had I sat there and finished them as I should have, they would be much better stories. Each time the story gets left unfinished, the magic seeps out and it becomes much harder to complete it. The inspiration disappears.
So, whether you find writing short stories hard or easy I think it is important to finish writing it in one sitting. Editing the story can take as long as necessary.