Life and Death

I am struggling of putting this serious topic in my second posts, yet it is things which is troubling me this few days.My grandmum's 80 years old sister is having serious condition after falling in her bathroom recently. She is in the intensive care unit for days, her condition is worsen, my grandmum decide to visit her, may be for the last time in her life. The next day when my grandmum left for hometown, i fall sick, first by flu due to infection, next by sore throat, then the miss consumption of antibiotic, induced gastric, i was in bed for two days. Now, anyone can tell me what is life? It is so easily taken just like that. The stop of heartbeat, the lost transmittion of brain cells and that is call death. I read a book from Tibetan about life and death, it said death is just a path which you have to pass thru when you are transform to another form of life, according to buddhism, there are many stage of life, reincarnation, which mean if you eat pig in this life, you might become a pig in your next life. If buddhism is true, that mean Death is the beginning to next life, and Life is the beginning of the death, so what is to celebrate when we have a new baby born in this world? and why we are so sad when somebody pass away? I so like this theory.