Parallel structure is an important function in writing because it can show a different idea to the story, it's different from POV (Point of view). All it really does is add a new idea into the story. Parallel structure can give your writing a negative impact  on your writing if you are to add too much detail or not enough detail. Also it can negatively affect it by if you were to add information that wasn't in your writing the first time. The last one it can affect you is by making look as if it was another point of view.