Mom dying of brain cancer pens heartbreaking letter to her young sons "What I want my boys to know when I’m gone."

 -- (Editor's note: Sara Chivers' goodbye letter to her children originally appeared on the Australian website The New Daily. It has been reprinted here with permission. Chivers' words have been shared around the world since her letter was originally published.

Chivers, 34, was originally diagnosed with brain cancer when she was 25. "I am living with terminal brain cancer," she said. "The question isn't whether I will die from this disease, it's when. It is this very question that has plagued me since brain cancer and I first made our acquaintance."

Since her original diagnosis, she married and had two children. Alfie, 18 months, was also diagnosed with brain cancer, though medical experts "believe a genetic connection between the tumors is unlikely." Her other son, Hugh, is 3. This letter is what she wants them to know when she's gone.

"Alfie’s diagnosis has given me a new purpose," she said. "Instead of sitting idle, I'll be using all of my might and willpower to give Alfie a voice. He needs me to champion his cause, to give hope where there is hopelessness. He needs me to be strong. He needs me to keep on living. He will be my legacy.")

Dear Hugh and Alfie,

I won’t be around to see you grow up. It’s a hard thing to say and even harder to face. You will have to hear from others the little things 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 better cook. I’m a keeper of mementos -- tiny hospital name tags, the poem Leigh wrote for my 21st birthday, first baby clothes.

I know your Dad, and our village of family and friends, will keep me alive for you as much as they can, but there are some things I want you to hear from me.

Don’t be afraid of expressing your emotions. I will never tire of hearing "I love you" from Leigh, you boys, my family, friends.

Love hard. As they say, it is better to have loved and lost, than never to have loved at all. That’s how I feel about you both. Heartbroken doesn’t come close to describing the pain I feel at not being in your lives in the future, but I would never change or forego the time we have spent together and the immense joy you have brought me. You are without a doubt my proudest accomplishments.

Pay attention to study but know there is so much more to school life than textbooks. Play team sports. Try a musical instrument. Learn a language.

Always try your best; I could never ask any more of you. Never fear failure -- you will learn more from mistakes than successes. There’s never anything more certain than change so embrace it. Don’t be afraid to try new things. Travel as much as possible -- it will shape who you are.

Be brave in your convictions and believe in yourself. Never tease or ridicule someone because they’re different to you. You will be a better person by surrounding yourself with people who will challenge your views and beliefs.

I can never emphasize enough the importance of good table manners. Remember to say please and thank you. Address your friends’ parents by Mrs., Ms. or Mr. unless told otherwise. Make your bed when you stay at other people’s houses, and always offer to clear their table and do the dishes.

You will have friends for a season, friends for a reason, friends for life. It won’t take too long to work out which ones fall into which category.

Family comes first. We will always be there for you to fall back on regardless of any mistakes or bad choices, and will help you through tough times and to celebrate life’s wins.

Be kind to your Dad. It won’t be easy for him raising you alone, but every decision he makes will be with your best interests at heart. He is an exceptional father and role model. Don’t let him doubt himself or the wonderful job he will do shaping you into the men I dream of you growing up to be.

There will come a time when he wants to find happiness again with a new partner. Accept and embrace his choice, and know she will be a positive female influence in your lives too. I have absolute faith that he will make the right decision, for him and you both, and I hope she enriches your lives as much as you’ve all enriched mine.

Your Dad is the most admirable, courageous man I have ever known. He is my companion, my rock, my everything. He has shown true grit in the face of our adversities, and without him beside me, I would have crumbled.

I will be forever grateful for the time we spent together, the memories we created, the love we shared. It was always him. Always will be.

Love,

Mum