Sometimes our candle goes out, but is blown into flame by an encounter with another human being.~Albert Schweitzer
The quote above made me think about the many times I've been stuck on a story. The idea is in my mind, half of it is written, and then it seems to go nowhere, or it goes skittering in far too many directions. Anyone who writes has been in a similar situation more than once.
So, as Mr. Schweitzer said, our candle goes out. And there we sit alone in the dark not knowing which way to go. Maybe that's when it's time to walk away, to go out and see what's happening in the world. Leave the story half-done and go for a walk, a visit to the library, or a trip to the mall.
Chances are that you will have an encounter with another human being. You might run into a friend you haven't seen for a long time, or have a friendly chat with a clerk. It's possible that a chance phrase or even a couple of words will trigger something to help you finish your story that's waiting at home.
Don't shake your heard. It does happen. I'm not going to guarantee that it will occur 100% of the time, but it can and does happen. Maybe the encounter need not be with a human being, maybe something you see while walking alone will trigger ideas for you.
Only this morning, a well-known author who shall remain nameless told her facebook friends that she had been stuck on a short story she was writing until the solution came to her in the shower. She left the story and did something not a bit related to her writing, and bingo--she had the answer.
The point of all this is to walk away when your writing becomes frustrating and nonproductive. Whether it's for an hour or all day, you'll have a better result when you come back to the unfinished story.