This is similar to the "Don't Break the Chain" method, which I think is attributed to Jerry Seinfeld (several articles have been written about this, google will help with an explanation). Another great technique, though this might not work as well for screenwriters, is an automated script for Google Drive, which I use for fiction writing. SF writer Jamie Todd Rubin has instructions on his blog (jamierubin net). The script runs overnight each day and can email you a count of how many words you write, how many consecutive days you've written, how many days in a row you've hit your goal, etc. It's a great way to keep track of how much I write; as Hemingway said "so as not to kid myself." I look forward each morning to waking up to see my writing streak has been extended just one more day.

Wow, that automated script for Google Drive is an interesting feature. Similar idea: Some objective thing we can see which provides a tangible sign of our progress. Thanks for that suggestion, Thomas. I do this with my exercise. I jog and bike, and I use Strava to track that, either using my iPhone (cycling) or GPS watch (running). It's such a great feeling to see that complete circle for each when I hit my weekly goals. Same thing for writing. I have a minimum page count per day I hit. I used to write per hour. Now I'm so busy with everything else, when I hit my page count, I'm done for the day, and off to other things. Again whatever works. In a nice bit of synchronicity, today's On Writing quote fits like glove on hand: “There are so many different kinds of writing and so many ways to work that the only rule is this: do what works. Almost everything has been tried and found to succeed for somebody. The methods, even the ideas, of successful writers contradict each other in a most heartening way, and the only element I find common to all successful writers is persistence—an overwhelming determination to succeed.” -- Sophy Burnham