There is an old saying in screenwriting circles that it never hurts to write about what you know. I suppose there's value in that advice, with one important caveat - sometimes it does hurt. Very much.

My sister Catherine's death from breast cancer at the age of 39 was a pivotal experience in my life. When she was diagnosed, I was working as a lawyer in Dallas, Texas, raising my kids and living my life, just trying to keep my head down and my eye on the ball. Catherine's illness changed everything. She was a young mother, in the prime of her life, and we were devastated. For five long years we watched her battle against the odds, and it was heartbreaking. Because cancer doesn't fight fair. There would be moments of hope and triumph, followed my moments of deep sorrow and despair. As a physician, my sister knew better than all of us what she was up against. And yet she handled herself with a steely grace and determination that was truly inspiring. She became our rock, instead of the other way around.

One night near the end of her life, I was sitting with Catherine during a chemo session, complaining about the law. She asked me what I really wanted to do and I told her I wanted to be a writer. She looked at me and said, "Well what are you waiting for? Look at me. I'm the perfect example that life is short." I had an epiphany. I quit the law, moved to Los Angeles with my (amazing) wife and kids, and pursued my dream of becoming a writer.

Cut to 13 years later. The Parenthood writers were gathered in the room, brainstorming story ideas for Season 4. When the idea of giving Kristina breast cancer came up, it was a loaded moment. Many of us on the staff have very personal experiences with the disease. We worried that it would be too depressing. We worried that it had been done before - and well - on other shows. But we had an ace in the hole - Jason Katims.

Jason is one of the most fearless writers I know. The character of Max Braverman comes from his personal experiences. His wife is also a breast cancer survivor, and if he was willing to go there, so were we. We felt that with Jason's guidance, we could take our viewers on a journey with Kristina that would be emotional, cathartic, sad, uplifting and even funny. But most of all - honest and real. I've never been prouder of a storyline or more in awe of our talented actors. Monica Potter and Peter Krause have been incredible.

I was thrilled when Jason asked me to write Episode 412. The emotional anchor of the episode is Kristina's decision to finally shave her hair after months of chemo. And man, that's some beautiful hair. I always felt this was a story about empowerment. I remember when my sister shaved her head, she told me it was a big fuck you to cancer. It had been controlling her life for so long, so she decided she wanted it to happen on her own terms - not cancer's. It's also a story about acceptance. Like Kristina in the episode, my sister didn't want to be defined by her illness. But by embracing it, at least in one small way, she was able to let go. And get through. For a while, at least.

I'd like to share a quick story about the episode's title. If you've experienced cancer, you know that people genuinely want to help. This can be both a blessing and a curse. In my sister's case, there was a group of family and friends who had started a prayer circle in her honor. A very nice thing to do, but it happened to come at a time when she was really struggling. Cancer has a way of shaking you to the core, and making you confront fundamental ideas like doubt and faith. Although we were raised in the Baptist church, I think in her heart, my sister was really a scientist. So when she heard about the prayer circle, she said to me, "You know what? You pray to God in a storm, but you keep on rowing."

Keep on rowing. I've always loved that idea. So... more than a decade after my sister's death, and inspired by my experiences on Parenthood this year, I decided to follow her advice yet again. I have started a breast cancer charity in her honor, called The Catherine H. Tuck Foundation. Our mission, on purpose, is very simple: to provide financial assistance to women in need who have been diagnosed with breast cancer. You can find our website at http://www.catherinefund.org. Please pay us a visit. Make a donation, share the link, help us help women who really need it. Your support would mean the world. And thanks for watching the show.

David Hudgins is a writer and co-executive producer on "Parenthood." His other credits include "Everwood," "Friday Night Lights," and "Past Life."