Quotes about loss
page 3

Misattributed
Source: Robert McAfee Brown https://en.wikipedia.org/wiki/Robert_McAfee_Brown. Preface for the 25th anniversary edition of Night https://en.wikipedia.org/wiki/Night_%28book%29. Page v, Bantam Books paperback; 1982 reissue edition.

“Grief, she reminded herself, is almost always for the mourner's loss.”
Source: Xenocide
“Even across the dark, even across the loss, even across the emptiness, soul will speak to soul”
Source: The Dark City

“With no loss or sacrifice, we can't appreciate what we have.”
Variant: With endless time, nothing is special. With no loss or sacrifice, we can’t appreciate what we have
Source: The Time Keeper

"Belief & Technique For Modern Prose: List of Essentials" in a letter to Arabelle Porter (28 May 1955); published in Jack Kerouac: Selected Letters 1940-1956 (1995) and in a letter to Don Allen (1958); published in Heaven & Other Poems (1977)
Variant: Accept loss forever

“Take what you can have. Rejoice in what you can save, and do not mourn your losses too long.”
Lews Therin Telamon
(15 October 1993)

Source: The Autobiography of Charles Darwin, 1809–82

“Why is the measure of love… loss? pg.9”
Written on the Body (1992)
Source: Why Be Happy When You Could Be Normal?
Source: Smooth Talking Stranger

“Though surely to avoid attachments for fear of loss is to avoid life.”
Source: We Need to Talk About Kevin

“Success consists of going from failure to failure without loss of enthusiasm”
Attribution debunked in Langworth's Churchill by Himself. The earliest close match located by the Quote Investigator is from the 1953 book How to Say a Few Words by David Guy Powers.
Misattributed
Variant: Success is the ability to go from one failure to another with no loss of enthusiasm.
Source: 1953, How to Say a Few Words by David Guy Powers, Quote p. 109, Doubleday & Company, Garden City, New York. Referenced by Quote Investigator http://quoteinvestigator.com/2014/06/28/success

“There is no teacher more discriminating or transforming than loss.”
Source: My Losing Season: A Memoir

Source: "Faulkner and Desegregation" in Partisan Review (Fall 1956); republished in Nobody Knows My Name: More Notes of a Native Son (1961)
Context: Any real change implies the breakup of the world as one has always known it, the loss of all that gave one an identity, the end of safety. And at such a moment, unable to see and not daring to imagine what the future will now bring forth, one clings to what one knew, or dreamed that one possessed. Yet, it is only when a man is able, without bitterness or self-pity, to surrender a dream he has long cherished or a privilege he has long possessed that he is set free — he has set himself free — for higher dreams, for greater privileges.

“It's a time of sorrow and sadness when we lose a loss of life.”

“That's the paradox of loss: How can something that's gone weigh us down so much?”
Source: The Storyteller

“As long as there is love and memory, there is no true loss.”
Variant: As long as there is love and memory, there is no true death,” he said. He
Source: City of Heavenly Fire

“There's a bit of magic in everything, and some loss to even things out.”
“Hell is the special pain that dwells in that loss which you yourself have caused”
Source: Seven Types of Ambiguity

“There's no great loss without some small gain.”
Source: Little House on the Prairie (1935), Ch. 25; said by Ma, after Pa lost the corn crop to blackbirds but brought home some of the birds for dinner.

"Imaginary Homelands (1992)
Source: Imaginary Homelands: Essays and Criticism 1981-1991
Context: It may be argued that the past is a country from which we have all emigrated, that its loss is part of our common humanity. Which seems to be self-evidently true; but I suggest that the writer who is out-of-country and even out-of-language may experience this loss in an intensified form. It is made more concrete for him by the physical fact of discontinuity, of his present being in a different place from his past, of his being "elsewhere"… human beings do not perceive things whole; we are not gods but wounded creatures, cracked lenses, capably only of fractured perceptions. Partial beings, in all the senses of that phrase. Meaning is a shaky edifice we build out of scraps, dogmas, childhood injuries, newspaper articles, chance remarks, old films, small victories, people hated, people loved; perhaps it is because of our sense of what is the case is constructed from such inadequate materials that we defend it so fiercely, even to the death.

Source: The Sickness Unto Death: A Christian Psychological Exposition for Upbuilding and Awakening

Katniss and Peeta (p. 388; closing words of the main text)
Source: The Hunger Games trilogy, Mockingjay (2010)
Context: I know this would have happened anyway. That what I need to survive is not Gale's fire, kindled with rage and hatred. I have plenty of fire myself. What I need is the dandelion in the spring. The bright yellow that means rebirth instead of destruction. The promise that life can go on, no matter how bad our losses. That it can be good again. And only Peeta can give me that.
So after, when he whispers, "You love me. Real or not real?"
I tell him, "Real."

The Clod and the Pebble, st. 3
1790s, Songs of Experience (1794)
Source: Songs of Innocence and Songs of Experience

Source: This Is How: Proven Aid in Overcoming Shyness, Molestation, Fatness, Spinsterhood, Grief, Disease, Lushery, Decrepitude & More. For Young and Old Alike.

“We are doomed to choose and every choice may entail irreparable loss.”

"The Wasp (Texas Radio And The Big Beat)" on the albums L. A. Woman (1971) and An American Prayer (1978)

“The loss of historical memory is restored in the very place where one has lost it.”
[Chouldjian, Bishop Sebouh, w:Sebouh Chouldjian, A bishops' pilgrimage to Western Armenia, The Armenian Reporter, 2009-12-12, http://www.reporter.am/go/article/2009-12-12-a-bishops--pilgrimage-to-western-armenia, 2010-06-16]
Other

Speech to University students (1959)

“We take no note of time but from its loss.”
Actually Night I, lines 55-56 of Young's Night Thoughts.
Misattributed

Source: Responsibility and Response (1967), p. 49
Preface
A Mathematical Dictionary: Or; A Compendious Explication of All Mathematical Terms, 1702

Source: (1776), Book IV, Chapter VII, Part First, p. 610.

Source: Leviathan Wakes (2011), Chapter 22 (p. 226)

The Cornerstone Speech (1861)

Source: The Intelligent Investor: The Classic Text on Value Investing (1949), Chapter II, The Investor and Stock-Market Fluctuations, p. 34

“And now it was your purpose to weep Vesuvius' flames in pious melody and spend your tears on the losses of your native place, what time the Father took the mountain from earth and lifted it to the stars only to plunge it down upon the hapless cities far and wide.”
Jamque et flere pio Vesuvina incendia cantu
mens erat et gemitum patriis impendere damnis,
cum pater exemptum terris ad sidera montem
sustulit et late miseras deiecit in urbes.
iii, line 205
Silvae, Book V

According to the Arab invaders who was Bhoja's enemy;[Kitsbul Alaq Al-Nafisa Part 4, Ibne Rustah]
About

Source: The 25-Year War: America's Military Role in Vietnam (1984), p. 165

Letter to Lucy Webb Hayes (25 October 1864)
Diary and Letters of Rutherford Birchard Hayes (1922 - 1926)
“My story is very boring. Mostly about hair loss.”
As quoted in "Debriefing Mike Murphy" https://www.weeklystandard.com/matt-labash/debriefing-mike-murphy (18 March 2016), by Matt Labash, The Weekly Standard
2010s

for example, the Jews in Poland
page 77 of 6 December 2012 publication by Springer Science & Business Media https://books.google.ca/books?id=nRArBgAAQBAJ&pg=PA77, translation by Mary J. Gregor (The Hague: Martinus Nijhoff, 1974)
page 238 of "Cosmopolitics: Thinking and Feeling Beyond the Nation" https://books.google.ca/books?id=4EmqLCWUFvEC&pg=PA238 in 1998, page 221 of "Acts of Religion" https://books.google.ca/books?id=c_kgAmFbvP0C&pg=PA221 in 2002, page 235 of "Spinoza's Modernity: Mendelssohn, Lessing, and Heine" https://books.google.ca/books?id=CYcOfkrduWYC&pg=PA235 in 2004, page 44 of "Friedrich Schleiermacher: Between Enlightenment and Romanticism" https://books.google.ca/books?id=IYVDMuOFN20C&pg=PA44 in 2005, page 8 of "The Jewish Odyssey of George Eliot" https://books.google.ca/books?id=juCYcPWdqccC&pg=PA8 in 2010, page 155 of "Inhumanities: Nazi Interpretations of Western Culture" https://books.google.ca/books?id=YMIsYMw0ES0C&pg=PA155 in 2012, page 75 of "Romanticism/Judaica: A Convergence of Cultures" https://books.google.ca/books?id=4svsCwAAQBAJ&pg=PT75 in 2016 and page 39 of "Cosmopolitanisms and the Jews" https://books.google.ca/books?id=6kk_DwAAQBAJ&pg=PA39 in 2017 also quote this.
Anthropology from a Pragmatic Point of View (1798)