For hundreds of years, this type of reminiscence was considered unhealthy. In the 17th century, a Swiss medical student named Johannes Hofer studied mercenaries in the Italian and French lowlands who longed desperately for their mountain homelands.
Witnessing their weeping and despondency, he coined the term nostalgia and attributed it to a brain disease. Other thinkers of the time echoed this view, and it persisted through the 18th and 19th centuries as well.
However, according to Dr. Chelsea Reid, an associate professor of psychology at the College of Charleston, United States, it's a mistake to assume that nostalgia leads to entirely dreadful symptoms.
In fact, "Unpleasant experiences, such as loneliness and grief, can arouse nostalgia, which can then help people cope more effectively with these hardships," she writes.
Thanks to scientific research, we now know that nostalgia also provides many benefits.
"It enhances feelings of optimism and inspiration and makes people view themselves more positively," Reid says.
"When people feel nostalgic, they feel a greater sense that their lives are meaningful."
Social benefits of nostalgia are especially well supported. It increases empathy and the willingness of people to give to those around them, such as volunteering for community events and donating to charities.
So in a way, creating and sharing posts like these is a form of public service. I know it sounds like a stretch, but the evidence is there!
Nostalgia also makes people feel more connected by reassuring them that they are loved by, connected to, and protected by their loved ones.
It also helps us to feel more secure in our close relationships and enhances relationship satisfaction.
Dr. Krystine Batcho, who is a professor of psychology at LeMoyne College in the US, says the beauty about trying to "pass on" and "infect" each other with nostalgia is that even if it doesn't work, it's not a negative experience.
"I never saw that [reminiscing about the past with in a group] can actually alienate other people because people don't necessarily want to hear about your nostalgic memories. They want to share their own," she explains.