黄粱一梦南柯一梦
[huáng liáng yī mèng nán kē yī mèng]
Both Huang Liang's dream and Nanke's dream are classic references in ancient Chinese fables. In both tales, main characters experienced short-lived dreams that brought about great ambitions or luxuries that turned out to be illusory. Therefore, this username suggests disillusionment or disappointment after an idealistic illusion fades away.