教授说了一个笑话,学员哈哈大笑。停了一会儿,他复述了这个笑话。这一次,仅有少数几个学员笑了。又停了一会儿,他第三次说了一遍这个笑话。这一次,没有一个人觉得好笑了。教授:“如果你们不能一再地因为同一个笑话而发笑,为什么要因为同一件悲伤的事而反复地咀嚼悲伤呢?” The professor said a joke, the students laughed. After a pause, he repeated the joke. This time, only a few students laughed. For a second, he said the joke again for the third time. This time, no one is funny. Professor: “If you can not laugh repeatedly because of the same joke, why should you chew and grieve repeatedly for the same sad thing?”