I don’t think any writer can ever fail in writing, nor can they “fail” when they publish. I personally think by the simple act of completing a first draft, a writer has done wonders. The problem is that my answer may seem a bit lighthearted.
Success can be defined very broadly, and a rather short answer to when you fail is writing is, well, if you tried and you had some success, then you didn’t fail. But when that book doesn’t get finished, is that a failure on the part of the writer?
No, not often.
A good writer can tell you that what they write is often not publishable. After a while, a good writer will say that 90% of what they write shouldn’t go much farther than a save on the computer for a cut and paste later… in a sense however, it is a “fail” but is it really a fail?
After you write and edit for many years, you begin to send out your manuscripts to agents and publishers, and you begin to get rejection letters. Everyone gets rejections letters, so this scenario is not something that few writers face. Still, it is a rejection, and someone somewhere doesn’t think your writing is worth their time or money. In a way it is a failure, but again is a failure like this one something that makes you stop writing?
Some writers do not get discouraged easily, and some do. This makes each writer unique, and the more you make the choice to push through the tough times, the more likely you are to see success; selling more books, writing more books, publishing more books is a way of “seeing” success.
That moment when you truly fail in writing is that moment when you, by your own choice, put away the
pen and paper, stop writing in general, or decide that writing for a living is not really for you. I consider that to be a true failure because any writer can learn to be better and see more success.