“He did not know that it was already behind him, somewhere back in that vast obscurity beyond the city” (180)
“...His dream must have seemed so close that he could hardly fail to grasp it.” (180)
Nick realizes Gatsby was chasing his dreams that were in the past.
Nick realizes Gatsby truly believed that his relationship with Daisy would be successful because of his strong desire and the amount of effort he put in. Although Nick came to the realization that it was doomed earlier on.