Another quotation I love is purportedly by Oliver Cromwell, once Lord Protector of England (in fact the only one we’ve ever had). He said:
He who stops being better stops being good.
I think these two quotations complement one another.
You can purchase an inexpensive copy of The Art of Worldly Wisdom book from Amazon or read it online for free via Google Books. The whole set of Wednesday Wisdom images can be found in my Creative Commons-licensed Flickr set.