Gatsby believed in the green light, the orgastic future that year by year recedes before us. It eluded us then, but that's no matter--tomorrow we will run faster, stretch out our arms farther ... And one fine morning- - So we beat on, boats against the current, borne back ceaselessly into the past." where in the book?

The excerpt is found in the last chapter, Chapter 9 of the novel. It concludes the novel.

Explanation:

"The Great Gatsby" by Francis Scott Fitzgerald is a tragic story of the protagonist Jay Gatsby in his pursuit of his previous love Daisy Buchanan. The twist in the story led to the deaths of Gatsby and myrtle, Tom's lover.

The above provided excerpt is from the last chapter of the story where Nick Carraway had gone back to Gatsby's place. There, he thinks of how Gatsby had blindly believed in the green light, 'the supposed bright future' that he had envisioned for himself and Daisy. These lines form the closing sentences of the whole novel, ending it.