“I now pronounce you man and wife.”
“We find the defendant not guilty.”
“Tonight’s winning lottery numbers are…”
Some things in life have a clear delineation between Before and After. You can circle that day on your calendar, point to that moment and say, “That was the instant one phase of my life ended and another began.”
Writing a book isn’t really like that. You can keep writing, revising and editing forever. Even when a deadline looms, there are always more changes that could be made… it’s not really finished. So how do you know when it is? When are you done? There’s an old story (perhaps apocryphal) about a museum guard who went through the galleries on his regular rounds. Though it was late at night, he came across a man daubing paint onto one of the masterpieces. The intruder was using quick little jabs of the brush, adding the tiniest of spots here and there. Exasperated, the guard said, “Oh, Mr. Picasso, not again! Can’t you please just leave it alone?”
The temptation to keep working on something is one that Robert Heinlein knew well. He guarded against it in his Five Rules of Writing. His Rule #2 is that you must finish what you write; tellingly, his Rule #3 is that (except under editorial edict) you must not go back and rewrite that which you have written. As with so many things in life, perfection is the enemy of progress. If you work to make something perfect, you’ll never get it out the door.
The question really shouldn’t be “How do you know when it’s finished?” That’s something that implies a definite endpoint, doesn’t it? No one can reach inside your head and flick the switch that will tell you it’s done. A better question would be, “How do you know when it’s good enough that you should stop messing with it and move on to something else?”
“But Tony,” you say, “you’re just dodging the question by rephrasing it! Your philosophical circumlocutions are amusing and all, but when do YOU call something finished? Or good enough?”
Fair question. I call something good enough when a) the deadline is upon me and I don’t have time to make it any better; b) when people I trust have told me what’s wrong with it and I’ve implemented changes to fix those issues; c) the editor says “That’ll do, Tony… that’ll do.”
Make it good, make it great, make it awesome… but don’t try to make it perfect.