The fruitive activities of a living entity oblige him to accept different types of bodies.
Although threatened from all sides, the deer simply eat grass in a nice flower garden, unaware of the danger all around him. All living entities, especially human beings, think themselves very happy in the midst of families. As if living in a flower garden and hearing the sweet humming of bumblebees, everyone is centered around his wife, who is the beauty of family life. The bumblebees’ humming may be compared to the talk of children. The human being, just like the deer, enjoys his family without knowing that before he is the factor of time, which is represented by the tiger. The fruitive activities of a living entity simply create another dangerous position and oblige him to accept different types of bodies. For a deer to run after a mirage of water in the desert is not unusual. The deer is also very fond of sex. The conclusion is that one who lives like a deer will be killed in due course of time. Vedic literature, therefore, advise that we should understand our constitutional position and take to devotional service before death comes.
According to the Bhagavatam (11.9.29):
labdhva sudurlabham idam bahu-sambhavante manusyam arthadam anityam apiha dhirah
turnam yateta na pated anumrtyu yavan nihsreyasaya visayah khalu sarvatah syat
After many births we have attained this human form; therefore before death comes, we should engage ourselves in the transcendental loving service of the Lord. That is the fulfillment of human life.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Fourth Canto, Chapter 29 – Text 53