A Country Doctor's Notebook by Mikhail Bulgakov (Harvill Paperbacks 1975)

'Clever people have long been aware that happiness is like good health: when you have it, you don't notice it. But as the years go by, oh, the memories, the memories of happiness past!
For myself I realise now that I was happy in that winter of 1917, that headlong, never-to-be-forgotten year of storm and blizzard.

(From the short story, 'Morphine'.)