One of the productivity tips that I have found useful is oddly from Ernest Hemingway (hardly a man of high productivity). He said that he always worked to a point where he knew how to continue, and then stopped working for the day. This way, he always had a good start the next day. I read about it in an article on creativity but didn’t know where it was from. I just discovered it’s from Hemingway’s memoir A Movable Feast, in a chapter about his interactions with Gertrude Stein (“Miss Stein Instructs).