Aggressive brain cancer is trying to end my life. The best doctors in the world are racing to find a cure. Meanwhile, legislation promoting assisted suicide all over the nation would dismantle essential protections and care on which I, and so many others, depend as we fight terminal illnesses. Bills that would legalize or expand assisted suicide have been introduced in 29 states.

Three years ago, I was living the American dream. I was happily married, our son had just turned 1, and I had a job I loved. My life changed in an...