When was the last time you listened to a cassette tape? Or rented a movie at a video store? Or did Halloween trick or treating, like in the good old days? It doesn't matter what decade you were born into, everyone feels a certain longing for the common, everyday activities we used to do in the past. Feeling sentimental for the times when people were nicer, life was easier, and the world seemed like (arguably) a better place than it is now is something that unites us all.

Reminiscing about the "golden ages" we’ve left behind us is also a thing that triggers our nostalgia response — a common, universal, and highly social-emotional experience. Seeing how certain objects or trends are fading into history inevitably makes us revisit personally meaningful memories and events we shared with loved ones.

But as Dr. Jesse Matthews, Psy.D., a licensed clinical psychologist based in Chester Springs, PA, told us in an email, we humans are not necessarily hardwired to feel these emotions, "but in many cultures nostalgia is certainly a thing."

Dr. Matthews explained that when we grow older, there is much less time for us to try out and enjoy doing activities that we like, particularly in a spontaneous way.

"When we’re young, much of our focus is on having fun, whether it’s playing with toys, hanging out with friends, or doing whatever it is that we want to do. But as we get older, most of us take on more responsibilities like careers, serious relationships, raising children, and having more bills."

"We can get very bogged down as well in the work and responsibility of life that we can even forget how to have fun," the psychologist added. This is why so many of us long for simpler times or days when things were more enjoyable. "I believe we all do this to some extent, recalling either 'the good old days' or particular things like places, people, and things like music, shows, and so forth."

Nostalgia is a powerful tool that usually helps us feel better about ourselves and even more in control of our current lives — if we manage to find a way to channel these emotions into the present. The longing for the past has a way to turn negative states such as sadness and loneliness into positive feelings that may leave us more motivated and passionate about our goals in life. Usually, but not always.

Psychologists at USC Dornsife College of Letters, Arts and Sciences found that nostalgia is actually a mixed emotion. Through their research, they discovered that in previous nostalgia-related studies participants were usually asked to recall past events that made them feel a sense of longing, which often led to them thinking about positive and fond memories.

"When people are asked to describe something that makes them feel very nostalgic, the positive elements dominate," David Newman, the study’s lead author and a Ph.D. candidate at USC Dornsife, said. "They think of a pleasant past experience, and the memories they bring to mind have a positive influence on how they see their own life."

So the researchers decided to conduct several studies to delve deeper into how frequently people may feel nostalgic and how intense these feelings get in their daily lives. After reaching out to 230 undergraduate students to participate in diary studies and complete daily questionnaires for 14 days, it turned out people were likely to feel nostalgic when something goes wrong for them in the present.

Newman explained this proves that this emotion can also be negative. What’s more, people reported feeling more stressed, depressed, and lonely on days when they felt nostalgic. They also expressed more regret and rumination, lower self-esteem, and dissatisfaction with their life. "These negative experiences colored nostalgia in a negative light,” Newman added.

But it’s not all gloom and doom. The good news is that the psychologists also found a positive connection when people "had helped others, were reminded of old friendships or music, felt inspired and engaged in social media use". And Dr. Matthews agrees by saying that nostalgia isn’t always a bad thing.

According to Dr. Matthews, it’s fun to reminisce about the past, especially with friends or other people our age. "It can become problematic, however, if we keep ourselves stuck in the past," the psychologist warned.

"In some cases, people are depressed because they can’t deal with getting older or with times changing, feeling as though nothing compares to how things used to be. A person can also be stuck on things like past relationships, as in the case of 'the one who got away.'"

It’s hardly surprising now that some people yearn for the bygone years, decry the contemporary world, and believe that the past was better than the present. And, ironically, they often complain about it online. As Dr. Matthews told us, all of this probably stems from bias more than anything.

"Many people believe 'their day' or when they grew up was in many ways better than the present day. The music was better, the fashion, or how people spent their time, for example," he said. "Nostalgia makes us feel emotional about these things and to view them more favorably."

Another explanation is that we humans also tend to focus on the good things rather than the difficult times we experienced in the past. "In some ways, life was simpler when we were younger, but through nostalgia, we tend to exaggerate this in a way that doesn’t exactly match the reality."

"Nostalgia or positive thoughts or feelings about the past can be a good thing, as long as we keep it in check," Dr. Matthews noted. "Reminiscing, daydreaming, or sharing stories about the past can be really fun, but just know that nostalgia is often biased and the reality of the past often doesn’t match our memory."

"If you find yourself dwelling in the past, however, feeling sad about it, or feeling unable to move on, then it might be a good idea to start looking at this. Finding some videos or books about it, self-reflecting or journaling, or talking with a therapist might be some good ways to get unstuck," Dr. Matthews concluded.