Don't let anyone make you believe that there are any rules in fiction writing -- except one: Don't bore your reader. Everything you do either tends to bore the reader or doesn't. You just need to know the difference and proceed with caution.
Equally worth noting is the fact that the words "never" and "always" aren't appropriate either when suggesting techniques or making choices as we write. When someone tells you, you must never do something, or you must always do something when writing fiction, you need to reject that advice.
What is important is knowing the consequences of your choices. Everything in the fiction business is about trade-offs. Every choice has a consequence.
For example: If you pick up the pace, you reduce the depth to which the reader can get to know the character(s). But if you slow down too much to paint a very detailed picture of a character, you risk losing the reader's interest because things are going too slowly.
Or, if you keep stopping the forward motion of your story to fill the reader in on what happened before the novel began (backstory) you slow down the forward progress of the unfolding story.
Or, if you add too many characters to your novel, you reduce the depth to which you can reveal all of them.
Or, if you switch POV in the same scene, you are quite likely to disorient the reader.
Or, if you write vainly, trying to show off your vocabulary with lots of 75 cent words, you are likely to distract the reader from following the story and cause him to focus on words on the page. This distraction pops your reader out of the vivid and continuous fictive ribbon.
So, when someone tells you something about writing, that sounds like an "always" or a "never" ask what the consequences of following the advice are. Then decide if it is worth it to you.
Here's an amusing truth about new fiction writers. They hear "consider" as "you must or mustn't." Quite often when I recommend a writer consider another option to some facet of his writing I will hear from him sometime later and he will preface his remarks with, "Back when I took your class on A you told me I can't do X (or I must always do Y, I should never do Z)..."
There are no always and nevers in fiction writing, only options with impact on your story.
Every bit of fiction writing advice starts with and ends with “Don’t bore your reader.” Every choice you make either follows that rule or breaks it.