Here’s a poem that helped me a lot when my own mother died (also from cancer):

Death is before me today
Like the recovery of a sick man,
Like the going forth into a garden after sickness

Death is before me today
Like the odor of myrrh,
Like sitting under a sail on a windy day.

Death is before me today
Like the course of the freshet,
Like the return of a man from the war-galley to his house.

Death is before me today
As a man longs to see his house
When he has spent years in captivity.

– Pyramid Texts (3000 BC)

Death is not extinguishing the light;
it is putting out the lamp
because the dawn has come.
Rabindranath Tagore
Poet, Philosopher, Nobel Laureate

Mary C. Philpott has written one of the most beautiful pieces of prose which encapsulates this concept.
I am standing upon the seashore. A ship at my side spreads her white sails to the morning breeze and starts for the blue ocean. She is an object of beauty and strength and I stand and watch her until at length she hangs like a speck of white cloud just where the sea and the sky come down to mingle with each other. Then someone at my side says: “There, she’s gone.”
Gone where? Gone from my sight, that is all. She is just as large in mast and hull and spar as she was when she left my side and just as able to bear her load of living freight to the place of destination.
Her diminished size is in me, not in her, and just at the moment when someone at my side says, “There, she’s gone,” there are other eyes watching her coming and other voices ready to take up the glad shout, “Here she comes.”
Dying’s part of the wheel, right there next to being born… Being part of the whole thing, that’s the blessing.

- Tuck Everlasting, Natalie Babbitt, 1975

Life was suddenly too sad. And yet it was beautiful. The beauty was dimmed when the sadness welled up. And the beauty would be there again when the sadness went. So the beauty and the sadness belonged together somehow.
- Dominic, William Steig, 1972

Condolences