We invest with these words at our core...

"It is a rule in Investing that you must not count
on the Opposition not coming, but always be ready for them;

that you must not count on the Opposition not attacking,
but make yourself so strong that you are invincible."

Michael Laulund (2010)
Sun Zi's The Art Of War for Investors

or said simply,

"never lose money" 
Warren Buffett