There are endless tutorials on fan fiction-related issues such as editing, paragraphs, outlines and such, but one of the topics that never get touched on is how to keep your story going in the same direction the entire time. Sure, your plot and outline can help with that, but your stories are told by the characters in them. So who's watching the characters?
What is character consistency?
Character consistency is the ability of the character to act in a consistent and predictable manner that moves the plot towards its conclusion.
That's a pretty simple definition for one of the most important elements in storytelling. One of the first rules of writing is that everything in a story must have a purpose. That means that all of your characters, regardless of how minor or major they might be, have a reason for being in the story. Their purpose should always be to m