The answer is: Forget about it. Put is aside. Find a nice shelf and put the manuscript on it and cover it with a pile of other, more interesting, things until you can’t see it no matter how hard you look.
In other words, forget it exists. Go on with your life.
Eventually, of course, your subconscious will begin to bother you. You’ll start searching your mental files to figure out what’s wrong. And then — eureka! — you’ll remember that novel you set aside.
More than likely, you’ll find that you have renewed interest in it and are more than happy to pull it out from the bottom of that pile and start working on it again.
Don’t know why this happens, I just know that, more often than not, it does.
The science fiction writer, Issac Azimov, normally had a large number of manuscripts that he worked on at the same time. Each day he’d look them over and decide what he’d work on at the moment. Which appealed to him. And, conversely, which had lost any and all appeal. He’d work on the ones that were interesting at the moment and ignore those that weren’t. And, if he tired of one story while writing, he’d switch to another.
Because that’s the way some minds work. By jumping around. And that’s okay.