As writers, we are constantly being told by the "experts" that we can't do this but we must do that. There are plot and structure rules, writing rules, grammar rules, querying rules and even rules for how to promote our books once we get to that stage. But this is probably one of the most lenient professions/hobbies where "rules are made to be broken." As long as you know the rules and respect them, you can choose to break them. Just be sure that when you do, it's the best choice for you and your story.
When you're in the first draft, such as in NaNoWriMo, though, you can completely ignore pretty much all those rules. Whatever has been broken can be fixed - if you want to fix it - during revisions and rewrites. It's not the time to be hung up on such details.
However, there are certain rules you absolutely, positively CAN. NOT. BREAK. I don't care who you are. Unfortunately, even the biggest and brightest authors do so. I'm talking about breaking the rules you've created for your own world.
What are the rules of your world? Well, they can be anything from how far away your protagonist and antagonist live from each other to what powers a supernatural or alien being possesses. Paranormal, fantasy and sci-fi authors probably create more rules for their worlds than other genre writers, but all authors have rules they create for their worlds.
When you break these rules, people notice and they will call "foul!" Authors such as J.K. Rowling and Charlaine Harris have had inconsistencies in their series and readers have noticed. Sometimes, these are little things that make readers say, "Ha! You messed up. I feel so smart." But sometimes, this breaking of your own rules can cause readers to say, "Bogus! That can't happen!" They feel cheated and even offended, thinking the author believed they could get away with it because readers are too stupid to notice.
I write characters with supernatural abilities and have created a world with my own take on paranormal creatures such as vampires, werewolves and mages. I have to be very, very careful to stick to my own rules. Sorcerers are more powerful than warlocks, who are more powerful than witches and wizards. Based on the rules I've set, it's highly unlikely one of my witches can beat a sorceress, so if that happens, I better have a damn good way of explaining it.
My characters' abilities also have parameters surrounding them - rules I can't change later simply because it's convenient. This can make writing hard sometimes, but just like we can't break the law of gravity in our world, as an author, I can't break the laws of mind-reading in my world if they've already been set.
As a prime example, look at Breaking Dawn Part 2.
***WARNING: THE FOLLOWING IS SPOILERY, SO I'VE WHITED IT OUT FOR THOSE WHO HAVEN'T SEEN THE MOVIE YET. IF YOU HAVE, PLEASE USE YOUR CURSOR TO HIGHLIGHT THE FOLLOWING TEXT TO READ IT.***
I caught a major flaw with the twist at the end of the movie that most everyone has called epic. I have to agree that what they added to the movie that wasn't in the books was amazing and the visual intensity was absolutely necessary because the books lacked it. Whether you're a Twilight fan or hater, no one can deny it's been a phenomenon and they could not end this with an anticlimactic scene like the books. Unfortunately, the world's rules were broken to do so.
I'm not talking about how the movie differed from the book. I thought it actually did well in keeping to the book, except for this one part, which like I said, was necessary and could have been awesome. So I'm not even going to refer to the books, especially since it's been a few years since I've read them. However, we just watched all the movies over the last week to prepare for this last one and they're fresh in my mine. Here's what I noticed.
In New Moon, Alice says she can't see Bella's future when Jacob is around, and also adds something along the lines of "I can't see past you and your pack of mangy mutts!" That is a rule set three movies ago - Alice can't see the future if the wolves are involved. In Eclipse, it's some of the same - Alice can't see the end fight because the wolves are involved. In Breaking Dawn Part 1, they're talking about the fetus and Alice says she can't see its future just like she can't see Jacob's. This has been a rule set and adhered to for three movies. Nothing has happened to change this rule.
So how, then, did Alice see the future of the whole fight that involved the wolves? She couldn't have seen Jacob and Nessie as they tried to get away. She couldn't have seen the wolves fighting the Volturi. She could not have shared that whole fight scene with Aro. And since Aro can see every thought she's ever had (a rule established in New Moon), he would know this flaw to her gift. So Alice couldn't have even made up the vision to try to trick him.
The writers (I include the author here because she's always been closely involved with the scriptwriting from what I understand), the director and the producer (who happens to be the author) needed to make the ending HUGE. EPIC. Talked about for months or longer. But the way they chose to do it broke their own rules, and they could only hope nobody noticed. Actually, I personally think they hoped everyone would be so relieved that all those people didn't die, they wouldn't care that the rules were broken.
But really, whether you noticed it before or just now see it, how does that make you feel? Cheated? Disappointed? A little angry? Ticked off because the makers thought you were too stupid or enamored to notice? Annoyed but you're okay with it because it was still an epic ending? I'm sure there will be people who feel any of these emotions and many others. My point to you is - how do you want people to feel about your own writing?
If you don't want anyone calling "foul!" or "bogus!" or "cheater!" then you can't break the very rules you have set. And if you find that you absolutely need to, then you better have a very good way of explaining how that rule can be broken. Maybe a necklace weakens or strengthens your character's ability. Maybe a time-warp has changed how your spaceship generates power. Maybe an earthquake creates a chasm that now requires your character to travel two hours to get to his best friend's house three blocks away. If you have to break a rule and can make it believable, just be careful not to do this more than once or twice. Otherwise, you come off as a lazy writer with poor planning skills.
Yes, rules are made to be broken. Even some grammar rules, like "don't use fragments and incomplete sentences." Sometimes breaking a rule makes the story or writing better. But unless you want to piss off your readers, never, ever break the rules you've created for your world. Because someone will notice and will out you.