The opposite of a profound truth is also true.

Whenever we’re creating something—an important report, a novel, a holiday newsletter—we face a crucial question that can be very hard to answer: When is something finished? When do you stop, when do you say, “I’m done?” How do you know you’ve done your best?

I love to find ways to cut, polish, tighten, find a better example or fresher metaphor, check for accuracy, add more humor, strike a more profound note—to make my work as good as I can possibly make it.

At some point, however, as I’m tinkering away, I begin to realize that I’ve entered the stage that’s often referred to as “rearranging the deck chairs on the Titanic.” Meaning, I’m making inconsequential changes that have nothing to do with the ultimate fate of my project. At that point, I need to let go. One of the most important steps in creating something is being willing to write “The End” and finish.

It’s a tough question: When do you think, “It can still be better,” and when do you decide, “It’s finished?”

I was intrigued by a story from the life of the acclaimed writer Shirley Hazzard. One of her most celebrated works is her award-winning novel, The Great Fire (Amazon, Bookshop) . It was 2003, she’d handed in her manuscript, and the galleys had been printed. For all practical purposes, the book was finished and out in the world.

Then she decided she had to change the ending. She wanted to give it a stronger sense of hope, so she reworked some phrases, she made a few additions—and most important, she added the final sentence, “Many had died. But not she, not he; not yet.” The changes weren’t extensive, but they changed the tone of the entire novel. Most authors would have thought it was too late to make the change, but she managed to do it.

To maintain the proper sense of engagement, to have the sense of the ending, is so, so hard to do.

A few times I’ve had a huge insight at the last minute, when it felt almost too late to incorporate it into my work—and I had to find the perseverance to re-open a project that felt closed, to mess with something that felt final, and to pursue a bigger vision.

In writing my book Life in Five Senses, I remember the moment when I was walking through the Metropolitan Museum, in a sunlit gallery full of marble statues, and the thought struck me, “The Met is my METaphor.” I had to re-conceive and re-write the conclusion of that book. Now that the book is finished, that paragraph (about the Met as my metaphor) is one of my favorite things I’ve ever written. But that insight came at the very, very end, and it felt like an enormous task to grapple with it and to rewrite such an important part of the book.

I want my project to be as good as it can possible be, and at the same time, I have to remember to step away from keyboard. At some point, I release my project if I want it to move on to its next stage.

The question is: When is that kind of last-minute work a waste of time, and when does it represent the indefatigable pursuit of excellence? It can be hard to tell, but it’s a crucial question.

If you want to learn more about my book Life in Five Senses, go to gretchenrubin.com. I have to say, one of my greatest strengths as a writer is my ability to write endings! Arguably, Life in Five Senses has two endings, and I love them both.