I always have several dozen works in progress. When I tire of one, or hit a wall or any kind, I stop working on that project and start working on another. I can always write something.
The upside of this method of writing is that I do not experience writer's block (and don't believe it exists, but I've said that too many times already).
The downside is that I can work hard, produce several thousand usable words, and still have no complete manuscripts to show for my effort.
Between Thanksgiving and Christmas I finished and submitted five new short stories. Since Christmas I've written many more words than I wrote in the weeks prior to Christmas, but I've completed no new manuscripts. I've written a sentence on this story, a paragraph on that story, a few pages on this other story, and have touched at least three dozen stories in the process.
So, even though I've been highly productive in terms of word counts and page counts, I've been quite unproductive in terms of completed manuscripts.
So it goes.