How far that little candle throws his beams!
So shines a good deed in a naughty world. -- The Merchant of Venice, Act V, Scene I
My Take - To a lot of people, a good act, even just a kind word to be polite, can mean a lot. We are bombarded, both by the media and in our lives, by darkness and conflict. By being good to someone, you bring a little light into their lives.