Last year I had a finished manuscript (MS) (edited and critiqued) that I sent queries out to a few agents on. I heard back from those agents with no. I set the MS aside and began a new MS for NaNo. Then, part way through NaNo, I thought I knew how to fix my MS, so I went back to it, but it still didn't work.
At this point, many would think I was completely discouraged. I had over two years of work into this novel and it still wasn't right. Instead, I put it away and started working on a companion novel for it. As I worked on this new MS, things started to shift in my mind for the original MS. And then, I had the breakthrough on how to fix what was wrong. Not only that, I had a way to better connect all three companion novels my brain was spinning.
I learned the value of walking away from a project, letting it sit while I worked on something else. How about you? Have you trunked a novel? Why and do you plan to go back to it?