I think it's the agony of knowing the inevitable, but it's prolonged over and over again. And though you don't want to see the inevitable you hope for peace. It's a stinking roller coaster ride. And it's actually traumatic and can be termed as that in a clinical sense.
My late stepdad was the person in my life. It started when I was in high school with kidney cancer(never mind the cardiac issues prior that disabled him shortly after my mom married him and moved out of state when I was around 12yrs old). Then in college it spread to his lungs and he was on oxygen. Then a couple of years after, it was penile cancer. Even the oncologist was affected by that surgery. He was quasi bedridden. Noticed in October, surgery that winter then all through that year(I had my first bout of optic neritus during this my own health was a mess) and he passed away a couple days prior to Christmas.
Long term illnesses destabilize life.