Nostalgia does have its painful side — it’s a bittersweet emotion — but the net effect is to make life seem more meaningful and death less frightening. When people speak wistfully of the past, they typically become more optimistic and inspired about the future.

“Nostalgia makes us a bit more human,” Dr. Sedikides says. He considers the first great nostalgist to be Odysseus, an itinerant who used memories of his family and home to get through hard times, but Dr. Sedikides emphasizes that nostalgia is not the same as homesickness. It’s not just for those away from home, and it’s not a sickness, despite its historical reputation.

Nostalgia was originally described as a “neurological disease of essentially demonic cause” by Johannes Hoffer, the Swiss doctor who coined the term in 1688. Military physicians speculated that its prevalence among Swiss mercenaries abroad was due to earlier damage to the soldiers’ ear drums and brain cells by the unremitting clanging of cowbells in the Alps.