I don't have the attention span to read novels anymore. Sometimes it feels like by the time I get to the middle of the book, I would have already forgotten the beginning. Reading short stories is instant gratification and has taught me much about writing economically. It wasn't until I actually started writing my own short fiction when I realized that, a. this is tougher than a novel. and b. short fiction and novels ask for a writer's different strengths. But the difference isn't as pronounced as, say, the difference between jetskiing and painting; it's like painting and digital art.
If you've been writing novels so far, I highly recommend following my blog posts over the next week or so about how to write a short story. The form is less forgiving in terms of shaky plotting, but if you've been struggling with writers' block, now's an opportunity for you to experiment with new ideas.