A force almost as powerful as love. Nostalgia is what you feel when you look back at the good times in life. The times you remember when you were at either your highest point or at least a memorable point in your past. The deadly thing about nostalgia is that you always enjoy an event more after it's already happened than when it's happening.
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.
A longing for the good old days, whether or not they were very good. Or:
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.
The realization when you go back to a special place, special activity or special thing from your younger life: that only one important thing has changed, and that that thing is you