“A cloudy day or a little sunshine have as great an influence on many constitutions as the most real blessings or misfortunes.”

Hassan Harbish and Colin Singleton, p. 128
An Abundance of Katherines (2006)

Source: Les Misérables

"Philip of Pokanoket : An Indian Memoir".
A more extensive statement not found as such in this work is attributed to Irving in Elbert Hubbard's Scrap Book (1923) edited by Roycroft Shop:
The Sketch Book of Geoffrey Crayon (1819–1820)
Variant: Little minds are tamed and subdued by misfortune; but great minds rise above it.

Characters, Ch. 2 : A Christmas Dinner
Sketches by Boz (1836-1837)
Context: Christmas time! That man must be a misanthrope indeed, in whose breast something like a jovial feeling is not roused — in whose mind some pleasant associations are not awakened — by the recurrence of Christmas. There are people who will tell you that Christmas is not to them what it used to be; that each succeeding Christmas has found some cherished hope, or happy prospect, of the year before, dimmed or passed away; that the present only serves to remind them of reduced circumstances and straitened incomes — of the feasts they once bestowed on hollow friends, and of the cold looks that meet them now, in adversity and misfortune. Never heed such dismal reminiscences. There are few men who have lived long enough in the world, who cannot call up such thoughts any day in the year. Then do not select the merriest of the three hundred and sixty-five for your doleful recollections, but draw your chair nearer the blazing fire — fill the glass and send round the song — and if your room be smaller than it was a dozen years ago, or if your glass be filled with reeking punch, instead of sparkling wine, put a good face on the matter, and empty it off-hand, and fill another, and troll off the old ditty you used to sing, and thank God it’s no worse. Look on the merry faces of your children (if you have any) as they sit round the fire. One little seat may be empty; one slight form that gladdened the father’s heart, and roused the mother’s pride to look upon, may not be there. Dwell not upon the past; think not that one short year ago, the fair child now resolving into dust, sat before you, with the bloom of health upon its cheek, and the gaiety of infancy in its joyous eye. Reflect upon your present blessings — of which every man has many — not on your past misfortunes, of which all men have some. Fill your glass again, with a merry face and contented heart. Our life on it, but your Christmas shall be merry, and your new year a happy one!

The Paris Review interview
Context: Many writers write a great deal, but very few write more than a very little of the real thing. So most writing must be displaced activity. When cockerels confront each other and daren’t fight, they busily start pecking imaginary grains off to the side. That’s displaced activity. Much of what we do at any level is a bit like that, I fancy. But hard to know which is which. On the other hand, the machinery has to be kept running. The big problem for those who write verse is keeping the machine running without simply exercising evasion of the real confrontation. If Ulanova, the ballerina, missed one day of practice, she couldn’t get back to peak fitness without a week of hard work. Dickens said the same about his writing—if he missed a day he needed a week of hard slog to get back into the flow.

The Conquest of a Continent (1933)

Source: The Works of the Right Reverend George Horne, 1809, p. 220 ; As quoted in Allibone (1880)

in "Lectures" (1894)