In The Great Gatsby, why does Fitzgerald leave the sentence "And one fine morning--" unfinished?

This reference to "one fine morning" appears in Fitzgerald's beautiful coda to the novel. Here it is in context:

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--

The implied conclusion to the thought is that on "one fine morning" our individual quests will end, and we will achieve our dreams. By not completing the sentence, however, Fitzgerald emphasizes the hope of achieving our dreams rather than the reality of it. The following, and final, sentence of the novel bears this out:

So we beat on, boats against the current, borne back ceaselessly into the past.

Dreams are not to be realized because they already have been ended, without our recognition, by forces beyond our understanding. This theme is realized in Gatsby's fate, as Nick interprets it:

. . . his dream must have seemed so close that he could hardly fail to grasp it. He did not know that it was already behind him, somewhere back in that vast obscurity beyond the city, where the dark fields of the republic rolled on under the night.

Although Gatsby's dream of Daisy was over even before he formulated it, he continued to pursue it. He dies waiting for Daisy to call . . . one fine morning.