“Never waste valuable time, or mental peace of mind, on the affairs of others—that is too high a price to pay.”

The Cost of a Laugh, Motion Picture Magazine, March 1918. http://archive.org/stream/motionpicturemag152moti#page/n75/mode/2up

Words of Wisdom (2010)

Des Moines Iowa speech (1 February 1916) http://www.combat.ws/S3/BAKISSUE/CMBT01N2/SMOKE.HTM, on "The Westerm Preparedness Tour" http://www.allthingswilliam.com/presidents/wilson.html
1910s

1980s, First term of office (1981–1985), First Inaugural address (1981)
Context: If we look to the answer as to why for so many years we achieved so much, prospered as no other people on earth, it was because here in this land we unleashed the energy and individual genius of man to a greater extent than has ever been done before. Freedom and the dignity of the individual have been more available and assured here than in any other place on earth. The price for this freedom at times has been high, but we have never been unwilling to pay the price.

2000s, 2002, State of the Union address (January 2002)

Special Message to the Congress on the Threat to the Freedom of Europe (1948)
Context: The recommendations I have made represent the most urgent steps toward securing the peace and preventing war. We must be ready to take every wise and necessary step to carry out this great purpose. This will require assistance to other nations. It will require an adequate and balanced military strength. We must be prepared to pay the price for peace, or assuredly we shall pay the price of war. We in the United States remain determined to seek peace by every possible means, a just and honorable basis for the settlement of international issues.

Herodotus: History (p. 45)
Classics Revisited (1968)