Editing. Just the word gives me hives. I hate it. I mean, I wrote a whole goddamned book, just to read it so often that I start despising it and changing it in ways I have never thought about? Yes, because you know what? Writing the book is the easiest part. Finishing your story? Piece of cake! But polishing it up to something worthy of another's eyes? Ugh... go away with THAT!
It's a process; something that starts small and grows over time. You begin noticing words you use too frequently, plotholes that glare at you from the pages and make you cringe and then there is the small matter of times you told where you could have showed. You realize that writing a book just isn't good enough, which is daunting and can lead you to give up. (Trust me, I have thought about it more times than I can count)
You sit there, pulling your hair, convinced that you are the worst writer since time began and your story isn't worth telling. This is the time where you should not listen to your inner wuss, but kick it where it counts. It doesn't matter that you wrote a 90k words pile of shite. You still wrote 90k words. That in itself is a reason to hold your head high.
Every story is worth telling and every story has at least one person who loves it. And that person should be you. For starters. More will come, trust me on this. Read through it with your head, edit, read it with your heart, edit, repeat. Ask people what they think, and not in a way that screams: 'I want you to tell me this is nice, if not keep your yap shut!' No, ask them what they really think, what they feel and be prepared for criticism.
Ah yes, criticism... You know what the great thing about criticism is? You learn from it. And not just about who likes your story and who doesn't; you learn about yourself. How do you react to it? Does it hurt you? Of course it hurts, it's your heartblood out there. If anyone doesn't like it, it will hurt. But there is not a single piece of anything creative in the world that everybody loves, so suck it up. Learn from it. Listen to what people say and listen to what many people say. If one person says your MC is flat and twenty others say they love him/her, guess which ones you should listen to. If one person raves about your stellar writing, but five others tell you that your grammar is horrendous and your tenses have been jumbled through a blender, guess again. You will notice that the more criticism you get, the more rational you'll be able to handle it. It gets easier, it just never gets easy.
It is said you should write what you know; I agree, to an extent. I say you should write what you love, what makes your heart race and a smile pop to your lips. If you write with passion, about something you love (be it genre, plot, whathaveyou) everything else will be a lot simpler. Your story will be better, people will feel the passion in your words and even the editing will go better. If you wrote a book because you think people will like it and you have read thousands like it so you know what you're doing, just imagine the following: You have to read and reread and change it and roll around in it for quite some time while editing. Do you really want that? With a book you think is okay and you think people will like? Or do you want to dip your head into a project you love with all your heart? The answer is simple. So write what you love.