“As long as you are convinced you have never done anything, you can never do anything.”

Source: City of Heavenly Fire

Succeeding in Science: Some Rules of Thumb (1993)
Context: Never do anything that bores you. My experience in science is that someone is always telling to do something that leaves you flat. Bad idea. I'm not good enough to do something I dislike. In fact, I find it hard enough to do something that I like. … Constantly exposing your ideas to informed criticism is very important, and I would venture to say that one reason both of our chief competitors failed to reach the Double Helix before us was that each was effectively very isolated.

Variant: If you’re always on time, it implies that you never have anything better you should be doing.
Source: Mistborn: The Final Empire

Variant: Because the world isn’t divided into the special and the ordinary. Everyone has the potential to be extraordinary. As long as you have a soul and free will, you can be anything, do anything, choose anything.
Source: City of Heavenly Fire

Source: Dilbert's Guide to the Rest of Your Life: Dispatches from Cubicleland

8 November 1944
My Day (1935–1962)

Source: The Sweetest Thing

Wonderful World
Song lyrics, Undiscovered (James Morrison album) (2006)