Oh, The Anguish!
There is nothing more daunting about writing than learning to write that first book. For me personally, it took years. Not that I didn't attempt to write novels when I was first writing. I started writing in high school and that blossomed once I got to college. What I lacked back then were two things: quality and discipline. I was still learning to write, so the quality of my writing was rather poor. Like any skill, it takes practice to become good at it. The more you practice - or do what you want to become good at - the better you get. I can definitely say that my writing now is magnitudes better than it was back then. But I still have a long way to go. My writing is something that will continually improve over time. (I don't know if someone like Stephen King believes that his writing improves over time... but I suppose I like to think that this very concept applies to every writer.)
Where I Started
When I first wanted to start writing, I didn't have any idea where to begin. I could write a term paper on some subject or another without too much trouble. I could even come up with ideas for stories without blacking out. But what I didn't have was the skills to do the actual writing. And the discipline to keep doing that writing from the exciting start, boring and sometimes anxious middle, and the glorious end! What I did learn in those early years of writing is that I could start small and then hope over time my writing skills would get good enough that I could coax a book out somehow.
NaNoWriMo
I never fretted about the writing in and of itself. I had stories I wanted to tell with my writing, but I didn't know what they were yet. The single most important thing I did for that first book was to meet a challenge I had. The challenge was to complete the book! I did it through a contest called NaNoWriMo (National Novel Writing Month). NaNoWriMo is a contest you have with yourself. The rules of the contest are simple: you have 30 days in November to write a 50,000-word novel. That's it! There aren't any entry fees or other requirements. Write a 50,000-word novel in 30 days or less. I did that very thing in 2007 with my first book, Rogue Planet. I used Microsoft Word to write it. I had a very general idea of where I wanted the plot to go, but no real concept of an outline or anything like it. Every day that month, I wrote at least 1,666 words per day. Later on, as I wrote other books, I would keep the status of my progress by using Excel. Each day, I would update the word count on my march to 50,000.
Another thing I remember with that first novel is feeling rushed at the end. I felt the plot had a certain pace and as I neared that 50,000-word mark, I rushed the plot along. It seemed like the novel should have been 60,000 words. But at the time, I was just trying to complete a novel, not necessarily write something that had a proper pace and ending. (As time went on, that was something I learned to do.) I also recall that many times during writing that first novel, I felt like my plot wasn't going anywhere and I didn't know what I was doing. It turns out that's something common amongst writers and typically happens somewhere between a third and two-thirds of the novel. It's during those times that you keep the course and continue to write past them. By doing that, you will complete your novel and be the writer you always wanted to be.