The other day I came across this quotation. It has stuck in my mind ever since:
"We are what we think.
All that we are arises with our thoughts.
With our thoughts we make the world.
Speak or act with an impure mind
And trouble will follow you
As the wheel follows the ox that draws the cart."
The Dhammapada (from a translation by Thomas Byrom)
Alberico Collina