MAKE THE RULES BUT THEN STICK TO THEM
If you’ve tried writing fantasy in any form—picture books, magazine story, chapter book, or novel—you know that a key element of fantasy is that things happen in the story that cannot happen in real life. Thus, you are deciding that your story will violate natural universal laws in some way. Some stories only slip outside the real world a little, and some create a totally extreme world that has little “normal” in it. But all stories abide by rules—you just get to decide what those rules will be.