One should try to understand the distress of accepting birth, death, old age and disease. There are descriptions in various Vedic literatures of birth. In the Srimad-Bhagavatam the world of the unborn, the child's stay in the womb of the mother, its suffering, etc., are all very graphically described. It should be thoroughly understood that birth is distressful. Because we forget how much distress we have suffered within the womb of the mother, we do not make any solution to the repetition of birth and death. Similarly at the time of death there are all kinds of sufferings, and they are also mentioned in the authoritative scriptures. These should be discussed. And as far as disease and old age are concerned, everyone gets practical experience. No one wants to be diseased, and no one wants to become old, but there is no avoiding these. Unless we have a pessimistic view of this material life, considering the distresses of birth, death, old age and disease, there is no impetus for our making advancement in spiritual life.

From Srila Prabhupada's purport to Bg 13.8-12