In his magnum opus, Thomas Wolfe writes,
...you can't go home again....You can't go back to your family, back home to your childhood, back home to romantic love, back home to a young man's dreams of glory and of fame,...back home to the escapes of Time and Memory.
In Chapter Six of The Great Gatsby, Jay Gatsby refutes Nick's observation that a person cannot repeat the past, "Why of course you can!" He does not know, as Wolfe points out, that he cannot go back to romantic love or the dreams of his youth. For, he cannot be the innocent young man that has met Daisy and fallen in love with her, not can she be in love with him as she was then.
In Chapter Nine, Nick broods after Gatsby's death, pondering Gatsby's illusions,
He had come a long way to this blue lawn and his dream must have seemed so close....He did not know that it was already behind him, somewhere back in that vast obscurity....
Thus, Gatsby's romantic yearning is predicated upon a false assumption of being able to reclaim the past. Gatsby's quest "for the grail" is but an illusion and the green light of the youthful, idealistic past is irretrievable. For, Time and Memory are ever-present and they effect changes. Gatsby's belief in "a promise that the rock of the world was founded securely on a fairy's wing" proves tragic as Daisy abandons Gatsby, in her struggle to remain innocent, implicating him as the murderer of George Wilson. It is only then, tragically, that Gatsby realizes "how grotesque a rose is."