Writing is a numbers game. Most of what you write will be crap. This applies to every writer ever. The problem with most writers is they think they need to make everything they write worth while. Most of what you write is going to be crap, so relax.
Think about your story. Frequently. This counts as writing. Work out every possible permutation, then think about it some more. Then get some sleep. If you forgot your idea, it sucked. That counts as crap writing.
When you actually write, write about three times what you need. Just write and keep writing. Then, get rid of half of it. Statistically speaking half of what you write will be below average, so toss out the half that is below average. You write 20k words, get rid of half of them.
After you get rid of half, now you have an okay story. Go back and pair out every word you don't need. 'Just' 'A bit' 'Slightly' words like that are filler. BE VERY SPECIFIC IN WHAT YOUR WORDS MEAN. Take the word 'Just' for example. Here's something you'll do.
He just stared at Her, "What the hell?"
NO. BAD. He didn't JUST stare at her. He stared at her AND he spoke so he DIDN'T 'JUST' ANYTHING. Just means he did one thing. He did two things. JUST is used WRONG. Get rid of just.
Do this for every word you write. Every word FOR YOU has a specific definition, meaning, and use. If you start using words incorrectly, your audience will know and they might not notice on a conscious level, it WILL gnaw at them. Like a sliver in their mind it will detract from your story. Know ever word you use exactly as it means to you and ALWAYS USE THE RIGHT WORD FOR THE RIGHT SITUATION.
Boobies. Breasts. Mellons, Bazongas. Tits.
They refer to the same subject, but each one has a different meaning. Furthermore, when a character is speaking how THEY view a word may be different from how you use a word. So when a character is speaking, remember to write from the character's perspective. Cunt might be offensive to you, but to an Australian, it's like saying 'crud' or 'phooey'. It doesn't mean the same thing to your character as to you, so what he 'says' must be from that character's perspective,
Know when to say, "She had nice breasts" and when to say, "She had amazingly mellifluous mounds of magnificently massive Mammalia!"
I use this example because it's breaking my own rules. I am using words incorrectly according to their specific meaning to me, but I am using them incorrectly because they all start with the 'M' sound, and that is part of the point. So understand that while you should be very careful about the words you use, you should also know that sometimes you have to break the rules for artistic reasons.
Periodically ask yourself, 'What is the worst thing that could happen here that would make sense and would likely happen?" Have that happen. It is good to ruin your MC's life. Make your MC suffer. We like to use the MC overcome adversity, so sometimes he/she/it should fail. Then figure out how the MC overcomes it.
Do not be afraid of easy solutions to problems. If you have established something in universe that makes is ludicrously easy to solve a problem, then don't insult the reader by not using it. SO BE CAREFUL WHEN MAKING YOUR MC TOO POWERFUL. It gets boring when the MC can fix everything just by thinking hard.
Guess what? The reader knows he is reading a story. He knows that you are not going to kill the MC. The Main Character is not going to be killed by the death trap. Don't bother trying too hard to convince the reader he's gonna die. The reader is more interested in HOW he survives. If you want to make the reader worry, focus on killing secondary characters, or Relationships where there is more than one choice for who is "THE ONE". Don't tear down a prospective 'True Love' to make it seem like the MC might choose the other 'True Love'. Build up the secondary 'True Love' to make it less obvious who the choice is.
Know your MC and how they think. When you write it, it is now cannon. You are stuck with it. He hates flapjacks? Then if he eats flapjacks later, there had better be a reason.
Conservation of plot: Try to have everything you write mean something. It is a metaphor. It is an allusion. It will come up later. It will be a recurring theme. Furthermore, when possible, have it serve double duty. For examples, I always look up the meaning of any name I give a character. The character has a name to refer to him as, but the name is also a hint as to what the character's purpose or meaning in the story is. Don't just make up names. The first name is most important, but the family name should be about the character's upbringing or environment. If you use middle names, it should be revealed at some point but indicate some sort of hidden aspect.
We come back to most of what you write is crap. If you write 3 times what you need, throw out half, you now can very slowly whittle down the rest of the story to get rid of excess words. Also, avoid using the same word twice. At most avoid using it in the same paragraph, but avoid using in the same chapter, if at all possible.
The word "Says" is no longer in your writing. Use a comma and quotes for spoken words.
Instead have some indication of what the character is doing.
He looked up, "Word"
He looked away, "word"
His eyes looked down, "Word"
He scratched his chin, "Word"
He Rolled a finger in the air, "Word"
He scratched his nose with his middle finger hoping only the asshole in front of him noticed, "Word"
He snapped his fingers, "Word"
"Word" He exclaimed as he fell into the vat of molten steel
He squinted with one eye and slowly tilted his head to the side quizzically, "Word"
Show, don't tell, when it is interesting.
Tell when it is boring.
He sat there in the library. Time passed. He slowly turned a page and then looked at the clock. Time passed. There were words on the page. He read them.
Boring.
The MC went to the library to study up on ways to kill the demon lord.
Tell when there isn't any 'action' so you can 3rd person omniscient narrative the information the reader needs so you can skip to the good parts that will catch their attention.
Making sure the reader is entertained is the point. Fuck that noise about 'writing for yourself' Why are you publishing on this website? IT IS SO YOUR MATERIAL CAN BE READ BY OTHERS. You are asking these people to GIVE YOU TIME FROM THEIR FINITE LIVES. Do not waste their time. Give them the most you can out of every word, every sentence, every paragraph, every chapter, and the story. Make the story something someone else wants to read.
This does not mean give it broad appeal. You can appeal to a very select niche group, but even for that group, you should write it to entertain them the best you can.
FINALLY.
JUST WRITE THE DAMN STORY.
Most writers get bogged down in 'It doesn't look right, or feel right.' Well, that's because what you wrote is crap. It's going to BE crap. So write and write and write. Take the parts you don't use and put them in a folder. Go back and steal ideas from the past frequently. This requires you to have years of rejected ideas to steal from, so if you don't have that folder, GET WORKING.
Then, after you have written it, thrown out half, carefully pared down to the most concentrated and efficient story possible.
...
sigh.
This part is gonna hurt.
Get a text to speech program. I recommend Text Edit, but whatever you got will do. Put your chapter in the program, put on your headphones, and LISTEN to what you wrote.
Oh god it is going to be painful.
And as you listen, pause, and FIX whatever horror of writing you just listened to. Keep listening until you can listen to the entire chapter in one sitting from the beginning without vomiting. THEN... FINALLY...
You can upload it.