One of the writing rules (and remember, they're not rules, they're price tags) is that at some point in your book (usually midway or 2/3 of the way) your character will have a "Dark Night of the Soul". All is lost. Everything is hopeless. Why go on?
As writers, I think we can write this and write this well because so many of us have that feeling about our writing. Who knows what causes it. Maybe a single crow* flew by and you didn't greet it? Maybe you got a harsh reception to your work? Maybe it was just a bad day.
Whatever the cause, you decide to give up writing. You might even give it up for a whole day (week/month/year). But you'll be back, because published or not, you're a writer. You write. It's what you do. And you know what makes the Dark Night of the Soul go away? Same thing as for your character. You take action and move forward anyway. No matter how hopeless it seems, or how outnumbered you are, you keep on moving forward.
And you know what? It gets better. I promise.
*Crow rhymes are fun.