realising the shortness of this life

I realised that I will die tomorrow or after some years but it is certain. This life is shortest. May be, my mother's death may have compelled me to think of death. Even, once I read one of the answers of Swami Vivekananda :"You must think of death for some days. It will surely make you worried and disturbed. Even though, you have to think of it for several days. Then, you will get that you are temporary and your truthful living starts from that day.". May be, it had shown some effect upon my thinking.
Later, I read an interview with Mother Teresa which was given in Times, to the one of the querries, she said : " we are not sure of tomorrow. We may die even in the sleep." All these cumulatively showed effect upon my thinking.
But I am right to think of it. It is not at all pessimistic and waste. It forced me to think of what to do then. I don't know as of now. But, it had started search for the purpose of this human existence in me.