A girl walks along a beach, throwing starfish back into the sea, when she meets an old man. The man asks the girl why she is throwing starfish into the ocean. She says: 'The sun is up and the tide is going out, if I don't throw them back they will all die.' The old man says, 'But there's a whole beach and it runs on for miles. You can't possibly make a difference.' The girl picks up a starfish and throws it back in the sea. 'It made a difference to that one.'
Found that recently in the terrific book, Business Stripped Bare, by Richard Branson.
It was sent to him by the charity, Starfish.