I am going to start by saying I consider myself a very rational person. I try not to let emotion effect my judgment. Everything I believe I have a good reason to believe, and I try to not have strong feelings on anything I lack information on.
So when I say that certain things you have to write by feel, believe me.
First, your style is going to be by feel, no other way to do it. It’s very easy to get nervous with trying to make your book sound like you, to invent or create a new style of writing. This can easily mean you get so worked up that you end up writing nothing, or go over the same chapter again and again.
Don’t worry about it, it will come with time. Just do what sounds good to you, and gets across what you want to get across.
I did not really have much of a style until I was hallway through the first draft of my book. I worried about it for a while then decided that worse case I could just change things during my second or third drafts (which I did for this reason, but not as bad as I thought).
Once you get far enough along you will just know that a certain passage feels right or not, trust your gut and don’t overthink it or spend too much time on too few words.
The second thing you have to do by feel is character’s voices. While this will require some thought, you don’t need to have it all worked out before you start your first draft. Think about it as you write and it will come to you. You might come to a passage and realize that a character is using words that are too big, or too small. Give it time and thought as you write your first draft and you will be fine.