Someone:
""窃以少年老成，中国称人之语也；年长而勿衰，英、美人相勖之辞也，此亦东西民族涉想不同、现象趋异之一端欤？青年之于社会，犹新鲜活泼细胞之在人身。新陈代谢，陈腐朽败者无时不在天然淘汰之途，与新鲜活泼者以空间之位置及时间之生命。人身遵新陈代谢之道则健康，陈腐朽败之细胞充塞人身则人身死；社会遵新陈代谢之道则隆盛，陈腐朽败之分子充塞社会则社会亡."
Roughly translated, Chinese people like to compliment young people for being mature, where as British and Americans like to encourage each to stay young while growing old. Young people are like the fresh and active cells of a body. If there is no metabolism and the old cells don't get replaced by the young ones, the body dies. Society works the same way.
Chen Duxiu said this in 1915. Nearly a century later, we are still trying to make young people boring old people."