Patti LaBelle Shares What She's Learned After Losing 2 Sisters to Lung Cancer

— -- Patti LaBelle is opening up about what she's learned after losing two sisters to lung cancer.

"Everyone should just realize that today is not promised to you ... or tomorrow," LaBelle, 71, told ABC News. "Live your life full and just have a great life and try to help someone on your way."

She added: "I pray I get through every day and that there's a tomorrow and if there's a tomorrow there's hope for me to do what I have to do."

LaBelle's sisters Vivian and Jackie were both diagnosed with lung cancer when they were in their 40s. "Within a year, they were gone," the singer said.

LaBelle said she "continued to work" during her family tragedies because it's what her sisters would've wanted.

In fact, she filmed the music video for her 1989 hit single "If You Asked Me to" the day after her sister Jackie's funeral.

"I didn't want to do the video because of the circumstances, but my sister was a big fan of mine, so she would've wanted me to go on and perform, which I did but it was not easy," LaBelle recalled. "It was her memory and her determination to make Patti LaBelle a big name; [it] was helpful knowing she would want me to do that."

Since then, LaBelle said she's often reminded of her sisters.

For example, the singer said she often sees butterflies, which remind her of Jackie. In her 2001 book, "Patti's Pearls: Lessons in Living Genuinely, Joyfully, Generously," LaBelle wrote about seeing a "little yellow butterfly" at the funeral.

"Now whenever I see butterflies I smile because I see her," LaBelle told ABC News.

The singer said her sisters are also the reason why she's lent her voice to the American Lung Association's LUNG FORCE initiative to raise awareness about the dangers of the disease for women.

"It's important to me because I have a voice, and some people know who I am so they might listen," she said of why she's participating. "That's what I'm hoping."