Okay, one of the things I love about "Once Upon a Time" is their handling of curses and their system of magic It is pretty consistent. That is very key in writing fantasy or science fiction-CONSISTENCY.
Sometimes magical rules evolve slowly -like the magic in Game of Thrones. It is much more elusive and mysterious, but in a way they are being consistent. Their magic is changing in their world, as is the world itself.
But your magical or science fiction tech rules and how carefully you construct them are very important in writing these genres. If you are not consistent with your rules and structure, you may be subject to the following annoyed scowl from publishers and critics-
Lesson done. The sun is shining in Seattle, I intend to go enjoy it.