“To be known so well by someone is an unimaginable gift. But to be imagined so well by someone is even better.”

The Unbearable Lightness of Being (1984), Part One: Lightness and Weight
Variant: For there is nothing heavier than compassion. Not even one's own pain weighs so heavy as the pain one feels with someone, for someone, a pain intensified by the imagination and prolonged by a hundred echoes.
Source: Identity

The Brighter Side of Human Nature: Altruism and Empathy in Everyday Life, 1990.

Anathemas and Admirations (1987)

Variant: It's far better to be unhappy alone than unhappy with someone — so far.
Source: On Being Blonde (2007), p. 52

Aphorisms of Sir Philip Sidney; with remarks, by Miss Porter (1807), p. 23. London: Longman, Hurst, Rees and Orme https://babel.hathitrust.org/cgi/pt?id=uc1.aa0000617332;view=1up;seq=53

"Andrea del Sarto", line 70
"Less is more" is often misattributed to architects Buckminster Fuller or Ludwig Mies van der Rohe. It is something of a motto for minimalist philosophy. It was used in 1774 by Christoph Martin Wieland.
Men and Women (1855)
Context: I do what many dream of, all their lives,
— Dream? strive to do, and agonize to do,
And fail in doing. I could count twenty such
On twice your fingers, and not leave this town,
Who strive — you don't know how the others strive
To paint a little thing like that you smeared
Carelessly passing with your robes afloat —
Yet do much less, so much less, Someone says,
(I know his name, no matter) — so much less!
Well, less is more, Lucrezia: I am judged.
There burns a truer light of God in them,
In their vexed beating stuffed and stopped-up brain,
Heart, or whate'er else, than goes on to prompt
This low-pulsed forthright craftsman's hand of mine.

Some Men are More Perfect Than Others (1973)

Source: A Dirty Job