Birthday card sayings include George Bernard Shaw's, "We don't stop playing because we grow old; we grow old because we stop playing" and Denis Waitley's, "View life as a continuous learning experience." There is also Bernard M. Baruch's, "To me old age is 15 years older than I am."
Some birthday sayings are thought-provoking, such as the John Adams quote, "There are two educations. One should teach us how to make a living and the other how to live." Pop culture quotes used elsewhere, such as Mr. Spock's famous "Live long and prosper" from "Star Trek" or Steve Martin's "That's all I need!" scene from the film "The Jerk," can also be used in birthday greetings. For children and adults alike, the famous Dr. Seuss quote, "Today you are you! That is truer than true! There is no one alive who is you-er than you!" from the book "Happy Birthday to You" is appropriate.
Birthday card sayings, themes and art can be chosen by the age or milestone of the recipient. For adults, some popular choices are over the hill, golden oldies and a countdown theme that incorporates the birthday celebrant's age in games and activities. A good saying for a card to such an event is, "Forty is the old age of youth; fifty is the youth of old age."