Former NFL player Devon Still and his daughter Leah on "survivor's remorse" after battling cancer, and how they're helping other kids

Former NFL player Devon Still was always tough on the field, but when his daughter Leah was diagnosed with cancer at 4 years old, he had to hone a different kind of toughness. Devon and Leah gained widespread attention for sharing their journey on social media, and after more than a year of treatment, Leah went into remission. 

But many children don't make it that far, and the Stills felt a sense of "survivor's remorse" that motivated them to help others. 

Devon Still was a defensive end for the Bengals when Leah was diagnosed with stage 4 neuroblastoma in 2014. In an interview with CBS News ahead of September's Childhood Cancer Awareness Month, both Devon and Leah said fighting cancer can be lonely and isolating.

"There's no playbook to battling childhood cancer or neuroblastoma," Still said. "There was nothing out there to help walk you through the steps on what to expect when your child is diagnosed, what to expect when they're going through treatment and what to expect after treatment."

Leah was given a 50/50 chance to live and went through dozens of rounds of chemotherapy, antibody therapy and radiation. At the time, her athlete dad had a simple mantra: "Win the day."

"When you look at the battle with cancer in its totality, it's kind of demoralizing," her dad told CBS News. "So, what we decided to do was just attack each day, to try to have fun and enjoy our life and the moments that we had together."

Still, 32, often danced and sang with Leah during her hospital stays. "Although I was a 300-pound defensive lineman with two left feet that don't know how to dance, whatever I had to do inside the hospital in order to put a smile on Leah's face, I was willing to do," he said. 

Sometimes it was difficult to see, but the Stills were not alone. About 800 children are diagnosed with neuroblastoma each year, according to Cancer.net, which is run by the American Society of Clinical Oncology. 

Almost 90% of neuroblastoma, a type of cancer that produces tumors from immature nerve cells called neuroblasts, is found in children younger than 5 years old. The five-year survival rate for neuroblastoma is 81%, but survival depends on many factors, such as the grouping of the tumor.

Leah, who is now 11 years old, is nearly six years in remission. "I was really excited and it was so important because I was finally cancer free. And it was such a huge relief," she told CBS News.

Devon Still said they met many children with cancer while Leah was receiving treatment, but sadly, many did not make it. 

"We both struggle with a lot of survivor's remorse," he said. "A lot of kids that we have met succumb to this disease. So that's why it really hits home for us, because there has to be another way. There has to be another way to help families to overcome this. We're tired of seeing kids die before they have a chance to live."

While Leah is now living a normal, healthy life as a sixth grader, she and her dad are still committed to raising awareness for childhood cancer. They founded the Still Strong Foundation, which provides financial support to families battling childhood cancer.

"It wasn't even a 'have to,' it was a 'want to.' Like we get to do this. It's a privilege, it's an honor to be able to be in this position," Still said. "It's a blessing to be in this interview, sitting with my daughter, who was diagnosed with stage 4 neuroblastoma and given a prognosis of a 50/50 chance of surviving. So it's not that we 'have to,' it's that we 'want to.'"

They've also partnered with "Braving NeuroBLASToma," a book series to help guide families through the harrowing disease. Still said it's the playbook he wished he had when Leah was diagnosed. 

"It gives the example to parents that you can still have fun, that you don't have to allow cancer to steal your joy. It's really and truly a game changer because it teaches families how they can keep their lives as normal as possible, although their lives have been flipped upside down," he said. 

Still said nothing can make cancer easy, but you can make it more manageable. He said in order to stay positive, families should "control your controllables." 

"We don't control the future, we don't control the past. We control right now," he said. "We did not let cancer steal our joy. We continued to have fun, we continued to enjoy life, we continued to attack the day. And when you mount up those small victories, they end up leading to bigger victories."

Leah said sharing your experience with others also helps. 

"You may think you're alone, but you're not, and I completely understand what you're going through. And sometimes it's hard to open up about it and I think that it's important to open up about it because me and my dad were very open to each other," she said.