Jogging is a sport with clear markers of success. As you run, and (if you are a beginner like me) tell yourself not to pass out, you can measure your efforts with landmarks. Run until that tree, run until you pass that house with the cute lawn gnome, run until you make it to the coffee shop on the corner… you can reward yourself easily as you go. This sort of exercise can feel very, very fulfilling.
What if writing could be like running? Could it be as rewarding? Of course! Creating markers for yourself as your write is one way to keep yourself on track as you write. Of course, this works best if you plot your story first, and not everyone works in this way. Another option, then, is to choose word counts as your marker.
100 words a day. Write your story in sections. 100 words a day for one week. 200 words a day for the next week. Similar to running, you need to build your endurance as a writer and build the habit. Creating a longer piece of fiction takes a certain amount of dedication. Treat it like a job- one that you love- and soon your word count will soar.