What is the purpose of life?

Jet lives a joyful life working at a factory with his girlfriend who he's deeply in love with. Shortly after they decide to get married and live together happily ever after her cat, who she has a weird affection for, dies. The girlfriend falls into depression which could (strangely enough) lead to her death and the only way to give her a purpose to live and save her is to tell her the meaning of life.