“Did you know that every Diet Coke takes 10 minutes off your life?” my daughters asked.

Their campaign to break my habit reminded me of myself at their age, on a crusade to get my mother to stop smoking three packs a day. My daughters never tried to flush my Diet Coke down the toilet, as I often did with my mother’s cigarettes, but their worry was the same. And although I generally only quaffed a can a day and did not poison them with second-hand backwash, I was the same as my mother: I ignored the concerns of my loved ones.

“Ten minutes!” I replied. “So what?”

I did a quick calculation. If I drank one Diet Coke a day for 40 years to come, that would mean 101 days off of my life. Double that, to allow for hyper-caffeinated days plus all the diet soda I’d imbibed since adolescence till this moment of truth with my adolescents. We were still only talking about 202 days off the long life I envisioned ahead of me.

“That’s way less than a year!” I told my daughters. “It’s worth it.”

Years passed as I merrily sipped away. Then I was diagnosed with a rare and aggressive form of uterine cancer. Different calculations preoccupied me: Would I see my daughters marry? Get to babysit their children? Make it to my youngest daughter’s graduation from college in a few months? How long till Christmas? I craved every one of those 202 days I’d been so blithely willing to forfeit. Every ten minutes might help me reach some important milestone.

I swore off Diet Coke the day I was diagnosed, and haven’t touched a drop since. It’s not that I think it caused my cancer (“If only figuring out what causes cancer were that easy!” said my Kaiser nutritionist). Since Diet Coke was about my only vice if you don’t count chocolate, I spend very little time blaming myself. Cancer happens. To a lot of us.

Since those dark early days, I’ve learned that my cancer was detected at the earliest possible stage, and that my prognosis is excellent. I should have many, many good years ahead of me. But they’ll be free of Diet Coke.

It’s my pledge to my daughters. I can’t promise them that I won’t eventually succumb—to something, if not cancer. But I can promise to give up Diet Coke.