Gray are all the theories, But green is the tree of life.
One errs as long as one strives.
He who does not know foreign languages does not know anything about his own.
Art is long, life is short; judgement difficult, opportunity transient.
We will burn that bridge when we come to it.
The affairs of the world are no more than so much trickery, and a man who toils for money or honour or whatever else in deference to the wishes of others, rather than because his own desire or needs lead him to do so, will always be a fool.