When my daughter Aaliyah was diagnosed with Ewing’s sarcoma in November 2016 at age 9, I was shattered, vacillating hourly between two nearly unspeakable fears: the fear that she would not survive, and the fear that during the last weeks or months of her life, she would suffer relentlessly.

Suddenly, thrust into a life I barely recognized, I struggled to navigate what moms who had gone before me kept assuring me would eventually...