All that is necessary for the triumph of evil is that good men do nothing. -Edmund Burke
It isn't what you eat-it's what you digest that make you strong. It isn't what you earn- it's what you save that makes you rich. And it isn't what you preach-it's what you practice that makes you a christian. -Francis Bacon
A new (to me) GK Chesterton on the mind:
Merely having an open mind is nothing. The object of opening the mind, as of opening the mouth, is to shut it again on something solid.