The concept of love is a universal one, transcending borders and cultures, and is often considered the foundation of any successful relationship.

However, maintaining a strong and healthy relationship over time can be a complex and challenging task, and many people wonder what the key ingredients are for a long and fulfilling partnership.

In an effort to gain insight into the secrets of successful relationships, the BBC invited couples to share their stories, and over 100 pairs responded with their own unique experiences and advice.

The responses revealed a wide range of strategies for keeping relationships strong, from navigating long-distance relationships to establishing non-negotiable habits like sharing a bed.

Certain themes emerged as common denominators among the responses, including the importance of honesty, communication, respect, forgiveness, friendship, and laughter in building and maintaining a strong relationship.

The most frequently cited advice from the couples was to work through conflicts together and to approach each other with kindness and empathy.

In celebration of St Valentine's Day, the BBC is sharing some of the love stories and lessons learned from the couples who participated in the project.

The chance meeting of Mik and John in a German nightclub in September 1978 was the starting point for a romance that would span decades, despite the fact that John was initially on a blind date with someone else.

Mik recalled being immediately drawn to John and making a mental note to pursue him, which ultimately led to a lasting connection.

However, their relationship was not without its challenges, and the couple faced significant obstacles in the early years, including physical distance and personal doubts.

John's military career took him to Ireland, while Mik remained in Germany, working as a nurse, and the distance threatened to derail their budding relationship.

John, now 70, remembered writing a letter to Mik during this time, which was forwarded to her by her colleagues, and proved to be a turning point in their relationship.

The letter helped to rekindle their connection, and the couple eventually reunited, going on to build a life together.

Today, Mik and John are celebrating 45 years of marriage, and they attribute their success to a combination of love, hard work, commitment, and luck.

According to John, a successful relationship requires a delicate balance of these factors, and the couple's experiences have taught them the importance of perseverance and dedication.

Mair and Alan Hicks, from Swansea, are another couple who have defied the odds, celebrating 65 years of marriage after meeting at a badminton club in the 1950s.

Alan, 88, advised couples to address conflicts promptly, rather than letting them simmer and potentially causing long-term damage to the relationship.

The couple acknowledged that they have had their fair share of disagreements over the years but have always managed to work through them and come out stronger on the other side.

Despite facing challenges and uncertainties, Mair and Alan have built a fulfilling life together, filled with shared experiences, including dancing, traveling, and raising a family.

Mair's philosophy is that as long as a couple is together, they can overcome any obstacle, and their relationship is a testament to the power of love and commitment.

Cris and Dave, who met online 25 years ago, have also faced their share of challenges, including discrimination and social prejudice, at a time when same-sex relationships were not widely accepted.

The couple recalled a difficult period when their property was vandalized, and they faced hostility from their community, but they persevered and supported each other through the tough times.

Dave, 54, credited Cris with providing a safe and empathetic space for him to express his feelings and frustrations, which has been essential in navigating life's challenges.

Cris, 59, emphasized the importance of empathy and reality checks in their relationship, which has helped them to stay grounded and focused on their goals.

The couple also highlighted the value of physical affection, such as hugs, in maintaining a strong emotional connection.

This year, Cris and Dave will celebrate 20 years since their civil partnership, a milestone that is a testament to their love and commitment to each other.

Cris remembered the moment Dave proposed, saying that it was a romantic and emotional experience that sealed their commitment to each other.

For Gary and Joy Walters, 54 years of marriage have taught them that humor is a crucial ingredient in a successful relationship, helping them to navigate life's ups and downs.

Joy, 72, acknowledged that their relationship has not been without its challenges, but they have always found a way to laugh together and support each other through difficult times.

The couple met while working at a toy factory in Cwmbran in the 1970s and have since built a life together, raising two daughters and learning to appreciate the importance of humor in their relationship.

Joy advised couples to address conflicts promptly and to always end the day on a positive note, with a kiss and a sense of closure.

According to Joy, a good sense of humor can be a powerful tool in diffusing tension and strengthening a relationship.

When Sahir met Dennis at a faith event in Cardiff over 20 years ago, they were both navigating the challenges of life after divorce and were looking for a new beginning.

Sahir, 49, described their journey together as one of growth and perseverance, marked by challenges and setbacks, but ultimately leading to a deeper and stronger connection.

Despite facing skepticism and criticism from others, the couple has proven their doubters wrong and will this year celebrate 20 years of marriage.

Sahir attributed their success to their ability to prioritize each other and work through challenges together, rather than letting them drive a wedge between them.

The couple has faced significant obstacles, including health complications and social prejudice, but they have always found a way to support each other and emerge stronger on the other side.

Sahir emphasized the importance of defying expectations and pushing past obstacles, and their relationship is a testament to the power of love and resilience.

According to Sahir, prioritizing each other is essential in building a strong and lasting relationship, and the couple's experiences have taught them the value of commitment and dedication.

Through their journey, Sahir and Dennis have learned to appreciate the importance of empathy, communication, and mutual support, and their relationship continues to grow and flourish as a result.

Sahir noted that the complexities of relationships often involve a mix of emotions, stating, "You're always going to love them, but you're not always going to like them."

A chance incident occurred when Carolyn was on her way to meet Carl over 30 years ago; a hammer fell from a five-story building, striking her on the head and resulting in significant bleeding, which led to an emergency room visit.

Carl, now 59, reflected on the unconventional start to their relationship, saying, "Most people would normally have a romantic start to their relationship."

Carl recalled the hammer incident, stating that it solidified his feelings for Carolyn, saying, "It took a hammer to make me realize how much I truly loved this person."

The couple, who reside in Blackwood with their three children, are set to commemorate 30 years of marriage this year.

Carl emphasized that love is not solely driven by emotions, but also by deliberate choices, adding, "Love isn't just a nice feeling, it's a decision a lot of the time."

The couple shared a laugh as they described their annual "professional development review," a practice where they assess the state of their relationship.

Carolyn, 50, mentioned that early in their marriage, they established certain non-negotiable principles, which have helped them navigate challenges.

According to Carolyn, these principles include never leaving the house during an argument, never sleeping in separate beds, and never uttering the word "divorce."

Zafar Khallyev and his wife Dilya have been apart for thousands of miles, residing on different continents, after being together for over 16 years.

Zafar, 38, acknowledged that the distance has presented significant tests to their relationship, saying, "Life has tested us with distance."

While Zafar pursues his PhD at Swansea University, Dilya remains in their native Uzbekistan, caring for their two children.

He attributed the endurance of their relationship to the qualities of trust and patience.

Zafar also emphasized that a strong relationship is not defined by its beginnings, but by the daily choice to prioritize one another, regardless of the challenges posed by distance or time.