“5344. Valour would fight, but Discretion would run away.”
Compare Poor Richard's Almanack (1747) : Courage would fight, but Discretion won't let him.
Introductio ad prudentiam: Part II (1727), Gnomologia (1732)
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Thomas Fuller (writer) 420
British physician, preacher, and intellectual 1654–1734Related quotes

2015, Speech: Declaration as Vice Presidential Candidate

“5324. Two Dogs fight for a Bone, and a third runs away with it.”
Introductio ad prudentiam: Part II (1727), Gnomologia (1732)

Referring to the National Party's problems with internal discipline and Robert Muldoon's reluctance to relinquish power.
Source: Gliding on the Lino: The Wit of David Lange, compiled by David Barber, 1987.

After fighting Axel Schulz in 1995. http://observer.guardian.co.uk/osm/story/0,,1053352,00.html

“For he would be thinking of love
Till the stars had run away
And the shadows eaten the moon.”
Source: Selected Poems and Four Plays

The Art of Poetry on a New Plan (1761), vol. ii. p. 147.
The saying "he who fights and runs away may live to fight another day" dates at least as far back as Menander (ca. 341–290 B.C.), Gnomai Monostichoi, aphorism #45: ἀνήρ ὁ ϕɛύγων καὶ ράλίν μαχήɛṯαί (a man who flees will fight again). The Attic Nights (book 17, ch. 21) of Aulus Gellius (ca. 125–180 A.D.) indicates it was already widespread in the second century: "...the orator Demosthenes sought safety in flight from the battlefield, and when he was bitterly taunted with his flight, he jestingly replied in the well-known verse: The man who runs away will fight again".