To take a page from Oprah, here's what I know for sure about writing: it's not a profession for the risk-averse.
I never know what my annual income is going to be. Not. A. Clue. Picture our financial planner's jaw dropping in shock.
I never know if my latest book is going to sell gangbusters, or languish on the shelves. I always think my books are swell, the hero and heroine fascinating and sympathetic, the villain well-motivated, and the plot interesting. But I also know that, despite my best efforts, other people may not.
I never know if this contract is going to be my last. (see above)
I consider these things the price I pay for doing what I enjoy. For being able to work at home, set my own hours, and be my own boss. This is also the nature of a career in the arts.
That said, I understand why people try to take the risk out of writing. They create "rules" and "musts" and "shoulds" as a means to try to increase the chance of getting published. They enter contests and join critique groups. They revise and revise and revise.
However, while rules, "musts" and "shoulds" may take away some of the perceived risk, I don't think they necessarily improve the chances of being published. Those rules celebrate the "tried and true," and while there are reasons for them, I think if you were to ask published authors, most of us break at least one or more "rules" all the time. Contests and critique groups, I fear, tend to reinforce the "rules." To be sure, they can help you to see and fix something that's not working in your story or with your characters, but they can also make you believe that what's unique about your work is wrong. Not different. Not interesting. Just wrong.
Revising too much can sap the energy right off the page.
I think the time you are most free to take risks with your writing is before you're published. There are no expectations, and letting your imagination run wild, breaking or ignoring some of the "rules," may actually increase your chances of getting an editor's attention and a sale.
Okay, let me draw back a bit. If you want to write a romance, there are certain conventions to which you must adhere, the focus of the story on the hero and heroine's relationship and ending with them together being the main ones. If you don't want to do that, you aren't writing a romance. Which is fine. Just don't try to sell it to a romance publisher.
And can't you cross a line between interesting and different to "What the--? Is this person nuts?" Sure, although nobody really knows where that is.
So I'm not advocating the wacky-for-the-sake-of-wacky here. I'm saying just don't think those "rules" are carved in stone. Unbreakable. Absolute. Or that you have to take anybody and everybody's advice about your story.
I also think you have to do what feels comfortable for you. If your imagination favors marriage of convenience stories set in Elizabethan England, go for it, even if somebody tells you Elizabethans don't sell. They may be right, but they may also be wrong. Your job is to tell the best dang Elizabethan marriage of convenience story you can, because your Elizabethan story might be "the exception that proves the rule" (a saying that makes absolutely no sense, if you think about it).
And if the only thing unique about your story is your voice, the way you tell the story? Nothing wrong with that at all. Just don't let anybody, including yourself, try to make your work "sound" like everybody else.
Now, for those folks who really like the security of rules, here are mine:
1. Be yourself. Tell your story the way you want. If you get a lot of feedback that your way isn't working from editors (ie people who can conceivably offer you money), then consider doing something different.
2. If a "rule" makes sense to you, use it. If it doesn't, forget it. Including mine.