I think the biggest obstacle writers face is trying to follow The Rules. Panic over following those bastards can lead to something worse: not being able to write at all for fear you're doing it "wrong." Thing is, they don't really exist, The Rules. They aren't really real. And there are far too many of them floating around, with a ridiculous amount of conflicting views for each.
Also, I happen to agree with many of those Fake Rules.
The most important thing you can do as a writer is to write the story, without thinking about anything other than the story, and writing it.
Then edit it. Then edit again, and again, ad nauseam.
Don't worry about whether it falls between 67,432 words and 72,333 words exactly. Just make sure how ever many damn words you have count. Every one of them (which is going to give the story the number of words it needs). *
Read each sentence as a separate entity and don't worry if you used "to be." Instead, ask yourself if that is the strongest verb you can use (sometimes it is).
Make sure you really need that adverb to get the point across (chances are you don't, but sometimes they work--voice comes to mind). **
In the end, those Fake Rules exist because they help with the craft of writing, but they won't help you write the story.
What do you think is the hardest rule to follow?
*The first time I stumbled across the word-count rule for genres-- after writing the horrid 150,000+ first draft of my first contemporary romance novel that I so thought was ready to be pubbed on the spot--I freaked out and went through my MS and deleted every extra "that" and contracted every possible phrase I could. This is not what's meant by cutting words. <cough>
**I happen to be a prolific adverb-voice user. This seems to happen with snarky female characters. And I haz those in spades.