Ugh. They’re everywhere, and often repeated as sage advice: “only write about what you know”. “Don’t use verbs other than ‘said’ to carry dialogue”. Some of these are useful in many cases, but should never be set in stone. If you feel it’s right to break a rule then break it. Better yet, act like their are no rules. I usually write “said” because it feels better. It’s not a rule, it just works. I try not to overthink it, as that would box me in creatively.
One of the frequently rolled-out lines is that “every character must WANT something”. Okay, sure, every human “wants” stuff and has motivation, but fretting over minor points with ancillary characters will bog down your story and may well induce writers block in many.
The better advice is this: you’re writing something that – I presume – you’d like people to read. That’s not too much of an assumption, right?
Well if this is true for you (and it almost certainly will be), then your readers are the masters, not your characters. Let your characters be who you want them to be. Go further: let them surprise you sometimes. It’s fun. But remember one thing: your READERS will WANT something. Maybe it’s a satisfying conclusion. Maybe it’s to be surprised and shocked. Maybe it’s to laugh out loud. Decide what it is you want your readers to feel and then… well, ignore it.
Seriously. As I said before, don’t overthink it. Let it sink to the back of your mind. It’ll come through subconsciously anyway when you write enticing scenes, or breathtaking dramatic moments.
Just don’t get hung up on writing rules. You’ll enjoy the writing process much more, and will probably write better things as a result.