SET A TIMER FOR 40 MINUTES
Don’t spend too much time on your opening.
Brainstorm for five minutes, spend the next five on an opening and then give yourself 20-25 to dig your characters into a hole and let them start to climb out of it.
Try to start wrapping it up when you have about five minutes left on your timer. Even if you have to write some brief notes [“this is where they make their great escape”], put an ending on the story.
This will make it so much easier when you come back to revise it later.
Full details at https://storyaday.org/2019-05-02.