Generally I have always been a novelist. I don't like reading short stories and I hate writing them.
That being said this foray into attempting to write a short horror story has been highly educational! I never would have expected to find writing horror not only educational but kind of enjoyable. I get to work with a new idea (that I can later turn into a novel) that I put all the important bits into one short scene that reads like a complete story. I think horror is a little easier to do this in since I don't actually have to have the good guy win in the end. Horror can easily be a tragedy.
Novels are usually much more intricate, have a larger cast of players, and more than one plot. You've got to pare a short story down to the most important plot (no subplots!) and maybe a tiny bit of backstory (preferably not much is needed) and a lot of action in a very short period of time. This is very challenging for me since usually my mind starts spinning new characters and plots and places... but it's a good exercise to bring that spinning down to a very tight spiral and try your hand at controlling your words and your characters as well as your situation. It's also nice because the story has a shorter end goal you can finish the initial draft faster and feel like you've accomplished something. If you're finding you're a little stuck and you usually write novels, why not try a short story as a "break" to let your story breathe but to continue writing!