One of my old favorites:
The best-laid plans of mice and men
often go awry.
Commentary thanks to Wikipedia
Based on Steinbeck's own experiences as a bindle stiff in the 1920s (before the arrival of the Okies he would vividly describe in The Grapes of Wrath), the title is taken from Robert Burns's poem, To a Mouse, which is often quoted as: "The best-laid plans of mice and men/often go awry," though the phrase in the original Scots of the poem is "The best laid schemes o' mice an' men/Gang aft agley."
And apparently the second poem falls into the poetic justice of the first as I can't get the formatting to work out so the poem is visible. Try Googling it instead: The Snark by Lewis Carroll.