A tendency to think that if you were twenty+ years younger, you would be happy -- as if you actually had been happy when you really were twenty+ years younger.
Student: "Get your pillow, Mr Nostalgia rides again."
Once upon a time, a man was born in 1947. His childhood in the 50s wasn't that good, but when he grew older, he started to hate anything past December 31 1959. Several years later, he gave birth th a child in 1967, who became nostalgic for the 70s, and said anything past December 31 1979 was awful, while his father hated the 70s because of nostalgia. The son later fathered a son born in 1987 with childhood in the 90s. The old man's grandon later said anything past December 31 1999 was crap.