There is often a high level of frustration with writing that makes an author want to bang their head against the wall, table, or floor. Sometimes translating a story from brain to paper is beyond difficult; sometimes it seems impossible.
I have tons of clearly defined characters in my head, but getting a reader to understand their various ticks, inclinations, and emotional complexity is daunting, to say the least.
I have been on both ends of the words. As a writer, it is hard to get the story out and then polish it into what it needs to be for audience consumption. As a reader, it is hard to wait for an author to get the story right so that you can absorb it into your imagination and share in the enjoyment--especially if there is a book series involved.
Deadlines are imperfect things when the creative mind is involved. As hard as I try to focus on one aspect of a story, another might tug at my mind to the point that if I don't write it down when it comes to me, I may never be able to recapture a detail. Also, trying to describe something on paper that you have only seen in your mind's eye may take finding the perfect words--perfect words result from lists of things that may clarify an image to a reader. Even if you manage to describe something perfectly. (in accordance with your thoughts) a reader's imagination may take the idea to another place.
Still, giving up will only drive a writer more insane than the writing itself.