I've posted these two rules one right after the other because of the way they go together. In his previous rule, Masello advises writers to let a manuscript sit for a day or two (or longer) before sending it out. But with this rule, Masello warns about the flip side, about writers who hold onto their work too long. Oddly enough, in this particular essay he doesn't discuss writers who revise their work over and over, although he does mention that type of writer elsewhere. Here he just mentions the phenomenon of a writer who has completed a manuscript and is just letting it sit in the house, even if editors are asking to see it.
Why does this separation anxiety exist? Masello suggests that the culprit might be perfectionism or a fear of rejection, but in the end it doesn't matter. If the manuscript doesn't get sent out, there's no way it can sell and eventually be published. And if the manuscript is timely, it's possible someone else will get to the idea and publish their own version before you do.
Although Masello doesn't focus here on perfectionism and fear of rejection, those are the two aspects of this rule that I'd like to discuss briefly. At times, I'm guilty of both. I constantly worry that the stories I send out aren't as good as they could be and that if I only had more time, I could make them even better. Well, that may be true, but the fact is that I don't always have the time. And if the story is of publishable quality and needs to meet a deadline, it's far more important to meet the deadline than to make the story perfect. There's an old quote that is attributed to Leonardo da Vinci -- "Art is never finished, only abandoned." Almost every writer I've discussed this quote with tends to understand what it's about.
As for fear of rejection, well, I understand that one too. Every rejection comes with emotional baggage, the worry that maybe you're no longer any good at writing, or perhaps you were never any good at it in the first place. But there's another famous quote, this one attributed to Robert A. Heinlein, that takes on rejection. One of Heinlein's five rules of writing is that you must keep a work on the market until it is sold. One way I've done that is by keeping a new copy of every submission ready to go the instant the previous one comes back as a rejection. That way, you have no time to marinate in your anxiety, and you really do end up seeing rejection as just part of the process.