“How many are there who live eleven months on the hope of the twelfth given to some brief but delightful wandering.”

Source: A Sand County Almanac, 1949, Foreword, p. vii (opening words).

Never Give All The Heart http://poetry.poetryx.com/poems/1545/
In The Seven Woods (1904)
Source: Poems
Context: Never give all the heart, for love
Will hardly seem worth thinking of
To passionate women if it seem
Certain, and they never dream
That it fades out from kiss to kiss;
For everything that's lovely is
but a brief, dreamy, kind of delight.
O never give the heart outright,
For they, for all smooth lips can say,
Have given their hearts up to the play.
And who could play it well enough
If deaf and dumb and blind with love?
He that made this knows all the cost,
For he gave all his heart and lost.

Source: The Secret Adversary

VII, 6
Meditations (c. 121–180 AD), Book VII

As quoted in a speech http://www.toad.com/gnu/cfp.talk.txt to the First Conference on Computers, Freedom, and Privacy in 1991

To Ernst Kaltenbrunner. Quoted in "Hitler and the Final Solution" - Page 137 - by Gerald Fleming - History - 1987
Undated

Source: Americanah

Litany for Dictatorships (1935)
Context: For those slain at once.
For those living through the months and years
Enduring, watching, hoping, going each day
To the work or the queue for meat or the secret club,
Living meanwhile, begetting children, smuggling guns,
And found and killed at the end like rats in a drain.

Page 17, cf. Theodore von Kármán (1957): "Everyone knows it takes a woman nine months to have a baby. But you Americans think if you get nine women pregnant, you can have a baby in a month."
The Mythical Man-Month: Essays on Software Engineering (1975, 1995)