In a moment of vulnerability, one mom opened up on Facebook about her teenage daughter's back-to-school anxieties.

What she didn't expect was that the message would gain traction across the internet.

PHOTO: Stephanie Cook pictured with her 15-year-old daughter Lucy Cook.
Stephanie Cook
Stephanie Cook pictured with her 15-year-old daughter Lucy Cook.

"It was pretty neat. I was surprised people were paying attention. ... I wasn't surprised at how good people are," said Stephanie Cook. "Some people said they read it to their kids the night before school started."

Her 15-year-old daughter, Lucy, was feeling nervous all summer about her first day of high school. Lucy, who has cerebral palsy, was worried about what others might think or say about her disability.

"Please consider taking the time to teach your kids about other kids like Lucy," the post read in part. "Teach them that Lucy has challenges every day that seem almost insurmountable, but the one thing she wants the most is to be loved and valued and accepted -- just like everyone else."

Lucy, who was born at 23 weeks and four days, also suffered a brain hemorrhage when she was a baby. Her mother called her a "walking, talking miracle."

After spending six years at a private school, Lucy was set to start at Higley High School, going from a small class size to just over 2,000 students.

PHOTO: Lucy Cook, 15, at a high school football game in Gilbert, Arizona.
Stephanie Cook
Lucy Cook, 15, at a high school football game in Gilbert, Arizona.

Her mother explained in her post that although Lucy has some special circumstances, her daughter's worries were not unique.

"Teach [your children] that they have the incredible power to build people up or tear them down, and they make choices with those effects every day. Be brave and reach out to those who look lonely," the post continued.

Since starting school, Lucy has three words to describe her experience so far.

"I love it," she told "Good Morning America." She added that her favorite teachers and new friends are like "Disney princesses."

PHOTO: Lucy Cook, 15, pictured with friends at a Higley High School football game.
Stephanie Cook
Lucy Cook, 15, pictured with friends at a Higley High School football game.

Cook said she wasn't surprised by everyone's kindness at school, and wanted to emphasize that the community has always been kind to Lucy and her family, but she was glad to share a message about "intentional kindness" and being aware that seemingly small things, like words, can really hurt someone.

"We just need to try to make it a habit to look for people that maybe need our friendship or give people the benefit of the doubt because everybody struggles with something," said Cook. "When [kids] realize this, they do better and they're there for each other."

She also added that having awareness around certain hurtful words, like the "R-word," is an important message "especially amongst teenagers, who can be unaware sometimes."

She said that all kids, her children included, need to remember two questions to help guide them through the ups and downs of the school year.

"I ask my kids ... every day after school," she said. "Were your friends nice to you today? And were you nice to your friends?"