Q Is For… Quotes!

I love quotes.  I have several quote dictionaries on my shelf, on subjects ranging from leadership to inspirational to a treasure trove for public speakers.  On Twitter, one of the popular hashtags is #quotes, and people from around the globe share things that inspire them.  There are many online resources, including BrainyQuote and Bartleby.  As a calligrapher, I like quotes to use as the genesis of an art piece.

What about you, Dear Reader?
What are some of your favorite quotes?