The Stories That Tugged at Our Heartstrings in 2015

— -- Though tragedy has struck so many corners of the world this year, there were also several heartwarming stories that restored our faith in humanity.

Here's a look back at the stories that tugged on our heartstrings in 2015:

Man Pens Powerful Letter of Defiance to Terrorists Who Killed His Wife in Paris Attacks

Even in overwhelming tragedy and lost, Paris resident Antoine Leiris found the courage to still love and live unafraid.

Less than three days after his wife of 12 years was killed in a of attacks in Paris on Nov. 13, Leiris posted an open letter of defiance on Facebook addressed to his wife's killers. The letter went viral.

"We are just two, my son and me, but we are stronger than all the armies in the world," he wrote. "He will eat his meals as usual, and then we are going to play as usual, and for his whole life this little boy will threaten you by being happy and free. Because no, you will not have his hatred either."

Read the full letter in English here.

Dad Refuses to Give Up Newborn Son With Down Syndrome Despite Being Threatened With Divorce

Samuel Forrest's baby, Leo, was born with Down syndrome. But immediately after seeing and holding Leo, Forrest told ABC News his heartbreak turned into joy. He said, "I looked at this guy and I said, he's beautiful -- he's perfect and I'm absolutely keeping him."

Though Forrest's wife told him that she would divorce him if he chose to keep Leo, Forrest stood by his newborn son.

"After what I've been through with Leo, I'm not going to sit back and watch babies be sent to orphanages," he said. "As a child with Down syndrome, that becomes somewhat of a label. If we can get around this label, we’ll see that they’re normal. They’re a little different from us, but they’re still normal.

Former Bengals Player Devon Still Announces His Daughter Leah Has No Signs of Cancer

In 2014, Leah Still was diagnosed with stage 4 neuroblastoma at age 4. But after nearly a year of intense treatment including chemotherapy and surgery, Leah was declared to be in remission in March just after her father Devon Still accepted the ESPYs Jimmy V Perseverance Award on her behalf.

And at the end of November, Devon Still announced on Instagram that he just got a phone call that Leah's "scans showed NED (no evidence of disease)! #LeahStrong."

175-Pound Pit Bull Shatters Misconceptions About the Breed

Though Pit Bulls are often regarded as fierce and violent, this 175-pound fella named Hulk proved this stereotype wrong earlier this year when online videos and photos of him playing and napping with his owners' three-year-old son went viral.

"My hope is that we can stop ignorance and change people's minds about Pit Bulls in a positive way with all this attention," owner Marlon Grannan told ABC News. "Because Pit Bulls are only in the media when bad things happen, this myth of them as monsters gets perpetuated, but it's not true. They might not be for everyone, but under a good leader and with proper training, they make amazing family and work or protection dogs."

Real-Life 'Notebook' Couple Dies Hand-in-Hand

California couple Floyd Hartwig and Violet Hartwig proved that the magical kind of love you see in movies does exist in true life.

After 67 years of marriage, the two died holding hands together at a hospice in February. Floyd had been keeping Violet company in the hospice, as her health deteriorated due to dementia.

Though the couple's death was sad, their children were encouraged by the lasting legacy of their love for each other.

"They weren’t fancy," one of their children, Donna Scharton, told ABC News. "They were just decent people that were always committed to each other, no matter the situation."

Florida Teacher Starts Each Day Complimenting Students One by One

This teacher deserves an A+.

Special education teacher Chris Ulmer spends 10 minutes at the beginning of each class to compliment his students one by one.

"I have seen their confidence and self-worth skyrocket," he writes in the video. "Every child deserves to feel accepted in this world. Instead of focusing on deficits, I focus on talent."

Ulmer told ABC News the change has been remarkable in his students, whose diagnoses range from autism to traumatic brain injury to speech apraxia to agenesis of corpus callosum.

"They all came from a segregated environment [from general education students]," he said. "Now they're participating in school activities, dancing in front of hundreds of other kids and are in the debate club."

Amazing Mosque Community in Ohio Helps Anti-Muslim Protester Undergo Change of Heart

A protester, who only identified herself as "Annie," arrived at Noor Islamic Cultural Center with signs showing Islamophobic imagery, but she left with new Muslim friends, a copy of an English Koran and a change of heart.

Despite over 40 minutes of resistance and sarcastic comments from Annie, mosque member Cynthia de Boutinkhar told ABC News she was persistent in her kindness and even hugged Annie, who then let "go of all that anger and fear" and finally accepted members' invitations to come inside for breakfast.

According to de Boutinkhar's Facebook page, Annie's parting words were, "You were all really nice. I don't approve of the violence or killings (neither do we), but I'll read this book. I had no idea Muslims could be nice to me, even after I stood out there with those signs. Sorry."

Ailing Father Gets Up From Wheelchair to Walk His Daughter Down the Aisle

Ralph Duquette was diagnosed with Leukemia in October 2012 and had to use a wheelchair after undergoing extensive chemotherapy. He told ABC News that when his daughter was engaged in August 2014, he was determined to find a way to stand up and walk her down the aisle. He had his doctor arrange home visits with a nurse and physical therapists to help him regain strength in his legs.

To the surprise of his daughter and her wedding guests, Ralph stood up from his wheelchair and walked his daughter Heather down the aisle.

“When she grabbed my hand I sort of felt safe and walked down,” Ralph Duquette said. “It was so amazing, she was so happy. It was something that every father dreams of.”

Air Force Veteran Reunites With Girl He Rescued During Hurricane Katrina 10 Years Ago

The three-year-old girl in this iconic photograph from Hurricane Katrina, which shows her bear-hugging the airman who rescued her, still has the same big smile 10 years later.

LeShay Brown, now 13, finally reconnected with Air Force Master Sgt. Mike Michael Maroney, who had been searching for her for a decade.

Maroney told ABC News that "words cannot describe" the feeling he had when he heard her voice again. He added, "I was like, 'Is this real? Is this really her?' I've been waiting for 10 years for this, and finally I found her. I had a stupid smile across my whole face the whole time."

Celebrations Break Out After Same-Sex Marriage Legalized Nationwide

Celebrations broke out across the U.S. and on social media after the Supreme Court ruled in a 5-4 decision that same-sex couples have the constitutional right to marry nationwide on June 26.

The majority opinion was echoed across the 50 states, where many uploaded photos, video and written sentiments of thrill, delight and festivity using the trending hashtag #LoveWins.

A video that went viral on Facebook caught one Kentucky woman's spontaneous proposal to her partner of over 24 years after they heard announcement of the Supreme Court decision.