I've often thought that being a writer compares to a marathon swim through the thickest molasses money can buy. One day the news is good and excitement fills the air, and the next day the dreams are shot down in the flames of rejection. One day you think the deal is in the bag, and the next day you find out that the dealmaker folded and went out of business. One day you are posting all over Facebook about a new project, and the next day you are told to put that project on the back burner because the market hates the concept.
It's hard.
And it doesn't get any easier even after you've successfully published fifteen books! The marathon continues, and the molasses are as thick as ever. It's a miracle every writer doesn't up and quit the race. But many don't, and won't, no matter how much disappointment, rejection and frustration they experience, because writing is what they were meant to do and they just don't know how to do anything else. Or they DO know, but can't find it in their hearts to do so. Swimming through molasses becomes preferable to a life lived otherwise, even though it might be an easier life with a lot less painful, sometimes brutal rejection.
Over the decades I've been writing, and selling, and not selling, I've learned that patience is both a virtue and a vice. I've learned that while you have little to no control over what happens "out there" once you are done with your work, you still need to stay in control. I've learned that each day will bring either joyful excitement, heartbreaking depression, or, at the very least, a lot of waiting and hearing nothing but crickets. I've learned that in order to be a writer, I've had to adapt to all these things, and more, and in the end be okay with all of it. I'm not always okay with it, but that's what they make wine for.
At some point, you get to stop swimming and take a nice, long breather. If you are lucky, you might even get to crawl out of the molasses for awhile and swim through something a lot lighter and more forgiving, like lemonade or chocolate milk. But each and every time you begin a new project, that threat is there, that promise of jumping back into the stickiness again, with all its possible excitement and acceptance, depression and rejection, disappointment and frustration and waiting and waiting and waiting.
The sooner you learn to like molasses, the better.