A life of happiness, unhappiness, or mixed feelings allows one to determine the proportion of virtuous and impious deeds in past and future lives. It is not very difficult to know one's past and future, for time reflects the contamination of the three attributes of material nature.
Currently, most incarnate spirit entities identify with their present body, the fruit of their past virtuous or impious deeds, and remain incapable of knowing their previous or future lives. Man indulges in sin because he is ignorant of the deeds of his past life that have brought him to his current condition, in a material body exposed to the three forms of suffering. He is seized by a desperate need for material pleasures, does not hesitate to sin, and commits reprehensible acts solely for the sake of satisfying his senses. All this is harmful, for as a result of his sins, he will have to receive another body in which he will suffer just as he now suffers from the consequences of his past sins.
The three forms of suffering are:
Those originating from the body and mind, those caused by other living entities, and those originating from material nature; hurricanes, violent winds, heavy rains, extreme cold, drought, etc., under the influence of beings from higher planets, which govern the various functions of material nature.
It must be understood that a person deprived of spiritual knowledge constantly acts in ignorance of what he may have done in the past or his previous life, what he is doing now, and how he will suffer in the future; he is plunged into darkness. This is why we must above all not remain in darkness, but strive to reach the transcendental light. This light is the spiritual knowledge imparted by Krishna, God, which can be known once one has attained the level of virtue, or when one transcends virtue by adopting the practice of devotional service offered to the spiritual master, the authentic intimate servant of God, and to the Supreme Lord Krishna. The meaning and scope of spiritual knowledge are revealed in all their fullness, and at once, only to great souls endowed with unreserved faith in God. Depending on our relationship with the attributes of material nature (virtue, passion, and ignorance), we obtain a particular type of body.