So what comes next for the writer, after yesterday's chocolate and tears and grieving for might-have-beens? There is a part of you which wants to curl up, give up, get out of the whole sorry business. But you are a professional. These things happen. You must carry on, or the bread on the table will be mere crumbs, fit only for mice, and there will be nothing to buy more with. "And anyway," says the sensible, practical part of you, patting the emotional, heaving part on the shoulder kindly, "look at what happens when you don't write. Think of the grumpiness and snarling and bad temper when there's a really good idea brewing, and instead of writing it down, you have to change sheets, or iron, or be a teen taxi or pay the bills or sort out mending or any of those other 'have to' things that live in the world outside your head.* And there was that other novel, remember. The one you were having trouble with, and then you suddenly had a brilliant idea about how to fix it? Why don't you haul that out of the folder and have a read?"
As a child, I had a horse-mad granny. Whenever I fell off, she would pick me up, plonk me back on, and we would carry on as if the fall had never happened, me having learned the lesson that falls mean bruises, but that bruises fade soon enough. It is neccessary to get back on the writing horse too, and sooner rather than later. Go back to something you like, and tinker with it. Play. Rediscover the fact that you actually like the act of writing, the challenge of getting words just so, in a way that says exactly what you want, how you want it. Write a letter. Write a poem. Write a blog. Just write. Because once you are back on the writing horse again, yes, the bruises still hurt, but you are high enough up that you can see the world ahead, stretching out in front of you. And you never know what treasure trove of ideas and inspiration might lie in wait just over the horizon. If you don't go forward, you'll never know--and it might be that idea which sells a million copies. As the Bard, (a useful man in times of trouble), said, "Sweet are the uses of adversity, which, like a toad, though ugly and venomous, wears yet a precious jewel in its head." Or, in more modern parlance, "Sh*t happens. Deal with it and move on."
*It has to be said that the activities of ironing and driving can, under the right circumstances, be quite good and fruitful thinking time--but you take the point. In my particular case, when I really want to write, beware the fool who gets in my way.