Then Vs. Now: 76 Pictures That Perfectly Show How Time Changes Things (New Pics)

Looking through photos of days and years gone by can often stir up deep feelings of nostalgia. And while this can sometimes bring us comfort and joy, it can also leave us feeling sad about what we've lost.

Interestingly, nostalgia was initially defined as a neurological illness characterized by a persistent longing for one’s homeland. It's a concept coined by Swiss physician Johannes Hofer back in 1688.

"It was not until the 19th century that nostalgia began to be seen as a positive sentiment, rather than a pathological condition," notes VeryWell Mind. But as we've already mentioned, nostalgia can be good or bad...

"Positive nostalgia is characterized by happy, rose-tinted memories of the past. It is often associated with feelings of warmth, happiness, and comfort," explains the site. "Negative nostalgia, on the other hand, is characterized by bittersweet or even painful memories of the past. It is often associated with longing, sadness, and regret."

On the plus side, feelings of nostalgia can help boost our mood, increase self-esteem, provide a sense of social support, help us to cope with difficult life transitions, such as divorce, retirement, or even the loss of a loved one.

But that trip down memory lane can also sometimes lead to a sense of loneliness and isolation, cause people to dwell on the past and become unhappy with the present, or make us less likely to take action in the current moment.

The trick, say some experts, is to learn to balance the positive and negatives feelings associated with nostalgia. To avoid falling into a "sad trap," those at VeryWell Mind suggest you think more about the present moment. Ask yourself: What am I doing right now that I enjoy?

"Make an effort to connect with others in the present. Spend time with people you care about. Talk to them about your positive memories," they add. "Do things that make you happy. Listen to music, go for walks, watch your favorite movie."

Of course, if you can't stop dwelling on the past and it's really affecting you, it helps to talk to a therapist.

Dr Valentina Stoycheva, a clinical psychologist and author, says nostalgia is a form of emotional regulation.

"I think of emotional regulation strategies as the spices we use to flavor our food," the expert writes. "If you use the right amount at the right time, you end up with a perfectly balanced dish. Too much salt, vinegar, or habanero, however, and the meal becomes inedible (and sometimes even harmful)."

Stoycheva says that while reflecting on the past can undoubtedly offer significant benefits for well-being, it only works when not taken to the extreme. She warns that too much dwelling on the past can lead to unhelpful behaviors and negative consequences. It can also stop us from using more helpful coping strategies.

"It is possible that overindulgence in nostalgia, much like overuse of salt or pepper, causes the present moment to be only colored by the negative emotions, in favor of glorifying some moment in the past," the expert explains.

Sometimes, the harmful effects of nostalgia aren't visible. But other times, they are. For example, if someone keeps obsessing over how their body once looked twenty years ago... They can't deal with the passage of time, and decide they absolutely must have surgery to keep themselves looking younger.

Negative nostalgia can also be seen at a societal level, says Stoycheva. She explains that this would be a case of people glorifying some historical past, without acknowledging the many cultural and collective traumas of that past, such as racism, homophobia, or other institutionalized human rights violations.

The expert says that it's important to ask yourself the following questions when you decide to go on a trip down memory lane:

1. What emotion am I after? In engaging in nostalgia, what former self-state am I seeking to recreate?
2. How will this help me and also how can I stay rooted in the present while I also feel the positive emotions of reminiscing?
3. Am I avoiding complex emotions? If so, what are they, and why are they so hard for me? Where else can I seek help in managing my emotions?

Again, nostalgia isn't all bad. So by all means, whip out those photos from years gone by. Just be mindful of why you're doing so, and what you hope to achieve. You might even find that reminiscing on the past you can help to improve the current you.

“When a person travels back to a productive or motivational time, the nostalgic emotions can help push them toward growth and future inspiration,” reveals Dr Kate Cummins, a San Francisco-based clinical psychologist.

“When you can look back on yourself 10 years ago and appreciate what you were while recognizing the truth in where you are, the progress you’ve made to get there, and the challenges you’ve overcome, this nostalgia is healthy and helpful,” Cummins adds.