Send a postcard to an old friend, and write a 100-word message on it. What are some of the things you tell them that you wouldn’t otherwise have said? How does the picture affect the language?
Length: 100 Words
Writing personal messages in limited space can help you concentrate important content, and help you do away with pointless miscellany.
Qwiklit 
I can definitely see the benefits of this exercise. I was forced to root through my brain and extract the true reason and tone of the message, not all the other things that are also floating around and associated with that particular person.I can see how it would benefit the writer when trying to decide what they want to convey in the space of a chapter or to decide the tone in a part of the story. Very helpful.