D their antonmys because they mean the opposite
It would help if I knew what book it was but I'm since I don't I am going to go with the fact that it is foreshadowing. Say yellow means happy as the sun well. We have the Yellow wallpaper yes. Say the yellow wallpaper starts to fade and pill that is the foreshadowing.
Maybe so you know it when/if it comes up later in school.
Explanation:
Nick said it because of his previous experiences which were not so easy to handle and that have transformed his thoughts so much that he considered that his future would be same as his past. He even didnt remember his birthday, indicating that his mind is well occupied by the menacing experiences and thoughts. Since he has turned thirty so now people think its time to settle but for Nick its still a road of struggle ahead of him