If you want to write a song, there are certain structures to follow. Unless you decide to break them all and create something brilliant like Ed Sheeran does...
If you want to produce a popular television show, be mindful of scale, number of characters, and the limitations of the small screen. Unless you want to produce Game of Thrones, the most successful television show in the world.
If you want to sell books, do it the way it’s been working for at least 200 years. Unless you want to create something like Amazon.com.
If you’re going to compose an opera, you have to do it keeping in mind the limitations of the human voice. Unless you’re Wagner, and want to make something that will still be inspiring people centuries later.
If you want to succeed in the male-dominated world of business, you have to play by their rules. Unless you decide to play by your own rules, like Barbara Corcoran, Arianna Huffington, or Oprah.
If you want to write timeless love songs, then follow society’s accepted practices about gender, sexuality and roles. Unless you’re want to do something magnificent like Sam Smith.
If you want to succeed in comedy, keep it safe, clean and politically correct. Unless you want to change the game, like Joan Rivers, Lenny Bruce, or George Carlin.
If you want to create a fantasy blockbuster, make sure to ground it in a believable reality. Unless you want to produce something epic like Harry Potter, DUNE, or Interstellar.
If you’re going to manufacture a utilitarian product like a telephone, stick to the basic functionality. Unless you want to create the iPhone.
When it comes to rules, here’s the only one that counts:
Know the rules, and be willing to break the rules – as long as you know why you’re breaking them.