Life is like a ten-speed bicycle. Most of us have gears that we never use.

Charles Schulz (1922-2000) American cartoonist

Peanuts [Linus] (1981-05-29)
    (Source)

The phrase was also used as the title in a Peanuts collection of Linus' wisdom, Life Is Like A Ten-Speed Bicycle (1997), which included this strip.