In chapter 5, Gatsby tells Daisy about the green light at the end of her dock. Why has he over romanticized her and how has this dictated his life?

Now that Gatsby has Daisy within his grasp, the enchantment wasn't the same. It seems the dream might have been better than the reality.

If it wasn’t for the mist we could see your home across the bay,” said Gatsby. “You always have a green light that burns all night at the end of your dock.”
Daisy put her arm through his abruptly, but he seemed absorbed in what he had just said. Possibly it had occurred to him that the colossal significance of that light had now vanished forever. Compared to the great distance that had separated him from Daisy it had seemed very near to her, almost touching her. It had seemed as close as a star to the moon. Now it was again a green light on a dock. His count of enchanted objects had diminished by one.