This article originally appeared on People.com.

Earlier this season, Sara Chivers learned that the mind cancer she has long suffered has become terminal, therefore the mom of two wrote a moving goodbye letter towards the boys she is going to leave behind.

“I won’t be around to see you develop,” Chivers, 34, writes to 3-year-old Hugh and 18-month-old Alfie within the letter originally published on The New Daily around australia. “It’s a hard thing to say as well as harder to face.”

Chivers, of Melbourne, Australia, beat brain cancer back in 2008, however the illness returned in March with Chivers suffering three tumors, Daily reports. She was undergoing treatment on one of the tumors when she and her husband, Leigh, learned that Alfie has brain cancer, though doctors don’t think there’s a genetic link between their two diagnoses.

“We were in a state of disbelief,” Chivers tells PEOPLE of the moments she and Leigh discovered their son’s condition. “It wasn’t even around the scale of our worst fears; it had been an inconceivable situation.”

In her letter, Chivers encourages her children to be brave, “love hard” and “be kind to your dad.”

“You will need to listen to others the little stuff that made me me: my perfume of choice is Michael Kors, my favorite meal is spaghetti bolognese, winter is my preferred season. I wish I was a much better cook. I am a keeper of mementos C tiny hospital name tags, the poem Leigh wrote in my 21st birthday, first baby clothes,” she writes.

“Heartbroken doesn’t come close to describing the pain sensation I feel at not in your lives later on, however i would never change or forego the time a year together and the immense joy you’ve brought me,” she continues. “You are certainly my proudest accomplishments.”

Chivers only agreed to be 25 when she was identified as having brain cancer, ABC News reports. She told ABC that she has long known the condition would take her lifetime. “The question isn’t whether I will die in the disease, it’s when,” she said.

She continued to marry Leigh and begin a family since her original diagnosis. And Chivers said her fight now’s for Alfie’s sake.

“Alfie’s diagnosis has given me a new purpose,” she told ABC. “Instead of sitting idle, I’ll be using our might and willpower to provide Alfie a voice. He needs me to champion his cause, to give hope where there is hopelessness.”

She added: “He needs me to become strong. He needs me to help keep on living. He’ll be my legacy.”

Chivers tells People who the response to her letter has been “overwhelming and humbling,” noting that they shared it to boost awareness concerning the “devastating impacts this brutal disease can have on families.”

“The most heartbreaking thing about my terminal diagnosis is the fact that I will not see my sons develop, and mother them like I usually dreamed,” she says. “My letter is a method to honor my impact in their lives and then leave behind a legacy for them.”

A GoFundMe page has been produced to benefit the family.