“Unhappiness. There are all kinds of unhappy people in the world. I suppose it would be no exaggeration to say that the world is composed entirely of unhappy people. But those people can fight their unhappiness with society fairly and squarly, and society for its part easily understands and sympathizes with such struggles. My unhappiness stemmed entirely from my own vices, and I had no way of fighting anybody.”

Все счастливые семьи похожи друг на друга, каждая несчастливая семья несчастлива по-своему.
Pt. I, ch. 1
Variant translations: Happy families are all alike; every unhappy family is unhappy in its own way.
All happy families resemble one another; every unhappy family is unhappy in its own way.
Variant: Happy families are all alike; every unhappy family is unhappy in its own way.
Source: Anna Karenina (1875–1877; 1878)

Source: Freedom

#110
1900s, Maxims for Revolutionists (1903)

Source: Veronika Decides to Die

Source: City of Bones

On amplifie également le malheur et le bonheur, nous ne sommes jamais ni si malheureux, ni si heureux qu'on le dit.
Modeste Mignon http://fr.wikisource.org/wiki/Modeste_Mignon (1844), translated by Katharine Prescott Wormeley, ch. XXIV: The Poet Feels That He Is Loved Too Well

Source: Is Everyone Hanging Out Without Me?