Why does the thin grey strand
Floating up from the forgotten
Cigarette between my fingers,
Why does it trouble me?

Ah, you will understand;
When I carried my mother downstairs,
A few times only, at the beginning
Of her soft-foot malady,

I should find, for a reprimand
To my gaiety, a few long grey hairs
On the breast of my coat; and one by one
I let them float up the dark chimney.

David Herbert Lawrence

http://www.poemhunter.com/poem/sorrow-3/