I think one of the biggest and most overlooked things to keep in mind when writing is: is how/what I am writing accomplishing what I am trying to accomplish?
Part of why so many writing "rules" don't work for everyone is that they're assuming you're trying to accomplish things that you're not trying to accomplish.
This way of thinking is applicable at every level and every step of your writing process.
Is this plot structure telling the story I want to be telling?
Does this scene evoke the emotion I am hoping to evoke?
Does this sentence mean what I intend it to mean, in a way that is likely to be read with that meaning by most readers?
If something in a story is jarring, for example, it's probably because that piece isn't accomplishing what you're otherwise trying to accomplish in the story.
When I talked about finding epithets jarring in a close third person POV, it's because what epithets do (provide distance from the character) inherently conflicts with what the point of view was intending (intimacy with the POV character).
If a scene or moment is jarring or just feels wrong in a book, it may be because it doesn't match the tone you are otherwise trying to cultivate, it breaks or escalates the tension in a way that you aren't intending, or it has a different narrative feeling than you are intending with the book.
Even down to the grammatical level, you can get away with breaking a lot of grammar rules if you can accomplish what you want to accomplish with the sentence. Is it coherent? Does it have the meaning you intend? Does it have the clarity or ambiguity that you are intending? Does it fit the tone that you are going for?
The same idea holds for the message/implication level. If you are implying or stating something in your story, is it what you mean to be implying or stating? If you are mimicking or subverting stereotypes, is it in a way that accomplishes what you are trying to accomplish?