Write 5-9 words. This is a 300% increase in writing over yesterday but I know you can handle it. Write the theme. Squeeze it into 5-9 words (AKA: “men are truly evil beings,” or “boys & girls can’t be buddies because of sex,” or “siblings are born to be rivals,” etc.) and type it. Next, cut it out and scotch tape it onto your keyboard or typewriter or screen. Thus, when you go to write your script you will always be reminded to keep it flowing through the 5-9 word theme.
"Man is his own worst enemy."
The theme of my script usually manifests after the first draft is complete. Felt weird doing it the other way around. Check out this great article by Bill Martell on Theme and Emotional Conflict.