For me with From Light to Dark and Back Again, this tends to lead to stories that end with a punch or where the reader knows the character is wrong (and a lot of the time would be about to be proved to be wrong if the story continued) and what I am after there is how knowing that makes the reader feel. Does the knowledge make them laugh (my light stories) or make them shudder knowing there is crime/horror to come (my dark tales)?
Thinking about what impact your story is going to have obviously directly affects how you write it but you can use this to strengthen the tale. Knowing you want to, say, write a funny story does dictate how you are going to present your characters but this is another reason to always outline what you think you are going to write before doing so. You can work out your options and then go for the one you like best.