Your eyes are so used to reading your work that they will lie to you.
From typos to misspellings, to strange sentences and questionable phrasing that you either wrote out wrong or tried to write while unable to sleep at 4AM, there will be times where you won't catch an error or awkwardness.
This also plays into that habit our minds have of filling in and autocorrecting extremely common words. Unless they're glaring mistakes, most of the time our minds and eyes decide that 'teh' means 'the' and you don't notice because they mutually decided "I will make this easier to read for you, buddy."
Then there are the times when you're reading a sentence and don't realize how it actually reads. Maybe you went back and changed a sentence, but didn't delete all the words. Maybe you deleted too much.
So what do you do? You run you work through an editing software to check for:
spelling
grammar
punctuation
how concise it is
Okay, cool.
Now read it out loud.
Reading your work out loud forces you to slow down. Most people read much faster than they speak and speed can backfire. Slowing down forces all the words to register. When you're reading your own work and forced to slow down and say each word, you will immediately stop as soon as you get to a word or sentence that sounds off.
Give your ears a chance to help you proof and edit your work.
Haven't you ever read something and thought "that sounds weird'? It can be grammatically correct, everything can be spelled right, but something about it is off.
THAT is what you are trying to find and fix.
Granted, this can also lean towards personal taste, but you're the one writing it so...shouldn't it be something you like to hear....?
Think about the tone of your story. Does the sentence you hear fall in line with the tone of your story; of that scene? You don't want it to sound comedic during a serious moment. The sudden change in the tone of a scene can be jarring to a reader and take them out of the story.
Think about the words used. Big words are awesome, but they're not always necessary. Are you trying to impress someone with your vocabulary or how you can transport them to another world with words? You don't want to use an uncommon word when there is a perfectly good common one. If it's an uncommon word that doesn't fit with the scene, it can draw the reader out of the story and break the flow.
Repeat words also stand out when you listen. Maybe you won't notice that you wrote 'and then' five times in the last two paragraphs, but you will when you hear it. It will give you the chance to go back and find different words or descriptions to use because you realized something was repetitive.
If you don't have time to sit there and read your 5k-10k chapter (don't judge me), then try downloading software that can read it for you. There are plenty of free ones and I can't really recommend anything, simply because I just use whatever I can get my hands on. Even the robotic, monotone voice can help make problem sentences and typos stand out.
In the end, hearing what you wrote is just another tool to help you edit it. It's not perfect, but when you're tired reading the same paragraph over and over and are lost in editing hell, give it a listen and see if you can catch anything you may want or need to change.
The change in editing method may help smooth out some rough parts and make your work sound better in the reader's (and your) head.
