What are the four tragedies in life?

There are four tragedies in China's classical dramas: Peach Blossom Fan, Dou Eyuan, Peony Pavilion and The West Chamber. There are four tragedies in China's Yuan Zaju: Dou Eyuan, Autumn in Han Palace, Wu Tongyu and The Orphan of Zhao. There are four tragedies in life: a teenager loses his parents, a middle-aged man loses his spouse, an old man loses his only son and has no mentor, and there is another tragedy: a long drought meets rain.