"Be who God meant you to be and you will set the world on fire." Anyone have the original Latin or Italian?

The Bishop of London quoted St Catherine of Siena's words at yesterday's royal wedding. I would really like to know the source, but don't know where it comes from, or indeed whether she wrote it in Latin or Italian.

2011-04-30T16:19:56Z

Superb answer Antonio. Grazie, grazie di cuore.

antonio2011-04-30T14:08:57Z

Favorite Answer

You find the original Italian sentence in St Catherine of Sienna's Letter.
From St Catherine to Stefano di Corrado Maconi. The sentence is:
SE SARETE QUELLO CHE DOVETE ESSERE, METTERETE FUOCO IN TUTTA L'ITALIA, NON TANTO COSTI.

The link is:

http://www.ilpalio.siena.it/Personaggi/LettereCaterina/default.aspx?Libro=5&Lettera=368