Happiness is like a pebble dropped into a pool to set in motion an ever-widening circle of ripples.快乐就像一块为了激起阵阵涟漪而丢进池塘的小石头。As Stevenson has said, being happy is a duty.正好史蒂文森所说，快乐是一种责任。There is no exact definition of the word happiness.快乐这个词并没有确切的定义，Happy people are happy for all sorts of reasons.快乐