Here we are on the other side of the Fourth of July. We’re in the heart of summer now, but I can feel its end and the coming of the crisp days of fall and then the biting winds of winter within the hot, sunny days that will still be ours for some time.

Book-length narratives—whether we’re talking novels or memoirs—are like that. The end is always contained in the beginning.

Think of The Great Gatsby, which opens with Gatsby longing for Daisy, with Tom Buchannan’s affair with Myrtle Wilson, with Nick Carraway’s romance with Jordan Baker. In Chapter 7, after Gatsby tries to convince Daisy to tell Tom she never loved him, Daisy, driving Gatsby’s car, hits and kills Myrtle Wilson. That moment is only possible because of what’s come before it. The narrative has built to this fulcrum. Beyond it, nothing will ever be the same. Think of a teeter-totter. A plank balances on a fulcrum. A rider’s weight makes the plank come down. Another rider’s weight makes it ascend. There is no back and forth in narrative. The story builds to a point beyond which the narrative has only one way to go, and that’s to its end.

Every other day, I run five miles on a treadmill. I used to run ten miles every day cross-country. Then my sciatica nerve told me I could no longer do that. So I get on the treadmill and I start out walking for a half of a mile. Then I start to run, increasing my speed at mile-long increments. In these early miles, I’m gathering speed. I’m rushing ahead even if I’m running in place. Then I hit the last increase in speed, and I know I can’t go any faster. At that point, my only choice is to maintain my speed, following step after step to the end.

Writing a book-length narrative is like that. It begins with a single movement on the page—a single step—and as it follows a series of complications for its characters it approaches, page by page, chapter by chapter, the plot event that will provide the fulcrum, that occurrence that will give the impetus for the final push of the storyline. Daisy kills Myrtle Wilson, and the path for the end of the novel is set—Daisy and Tom’s escape to Europe, George Wilson’s murder of Gatsby, Nick’s return to the Midwest. The end of the book swings upon the fact that Daisy hits Myrtle Wilson with Gatsby’s car.

At some point in our writing process, we’d be wise to think about what that fulcrum event will be. If you’re writing memoir, you might identify a particular time period of your life—your high school years, for example—and you might think of the one thing that happened that changed everything for you. That’s the event you’re moving toward through the early chapters of the book. It’s the same for novels. A tangle of your characters’ desires and actions lead to a moment of consequence. All you have to do is follow the aftermath of that moment to its significant end.

I hear from a number of folks who want to write either a memoir or a novel, but they’re paralyzed by the fact that they don’t know how to give the story a shape. I’ve just described one way. I hope it proves helpful.