There are a lot of tricks attributed to Hemmingway and this is one I use quite a bit. If you are working on something in more than one session, stop your work in the middle. Mid-sentence, mid code, mid visualization. Stop and walk away. The incompleteness of your work will get you motivated to jump right back in and finish.
What is happening when you stop in the middle? There has been quite a bit of research on this topic and it is known as the Zeigarnik effect. The Zeigarnik effect (named for Karl Zeigarnik), finds that people have better memories of incomplete tasks, or framed another way, an interruption during a process will improve memorability and motivation.
Give it a try and let me know your story.