Hope for the best.
Expect the worst.
The world’s a stage.
We’re unrehearsed.

Mel Brooks (b. 1926) American comedic actor, writer, producer [b. Melvyn Kaminsky]

The Twelve Chairs, “Hope for the Best, Expect the Worst” (1970)
    (Source)

(Source (Audio)). More information on composition of the song here and here.

See Cicero (44 BC), Shakespeare (1599), Heywood (1612), Billings (1877), O'Casey (c. 1940), Watterson (1993).