Five favorite quotes

A reader asked me if there were any quotations that served as a source of inspiration for me. While I’m not entirely sure how much inspiration I derive from them, I maintain a list of favorite quotations on my desktop that I add to from time to time.

The following have been rated as my five favorite for a very long time: 

Tears are not arguments. -Machado de Assis

Don't say you don't have enough time. You have exactly the same number of hours per day that were given to Helen Keller, Pasteur, Michelangelo, Mother Teresa, Leonardo da Vinci, Thomas Jefferson, and Albert Einstein. -H. Jackson Brown, Jr.

The problem is not that there are problems. The problem is expecting otherwise and thinking that having problems is a problem. -Theodore Rubin

Irreverence is the champion of liberty and its only sure defense. -Mark Twain

Sometimes I think we're alone in the universe, and sometimes I think we're not. In either case, the idea is quite staggering. -Arthur C. Clarke