Our past actions weigh us down today, and our present actions prepare us for future suffering. Thus, faults and sufferings follow one another, plunging the embodied soul, conditioned by matter, into pain life after life. In this life, it suffers the consequences of actions committed in its previous life, and prepares, through its present actions, new sufferings in the future. “Mature” or “completed” faults, which occur now, can result in chronic illness, legal troubles, a low birth, insufficient education, or a mediocre physical appearance.
The cause of all diseases is spiritual in origin. This cause is the forgetting of our loving relationship with Krishna, God, the Supreme Person. The soul that loses contact with God forgets its own spiritual identity and engages in countless material activities that entangle it in a network of karma, of actions and reactions. This karma causes it suffering, and instead of turning to God to alleviate its pain, the soul seeks material solutions which unfortunately lead to other karmic reactions, and therefore other sufferings.
Only loving and devotional service offered to God can put an end to suffering and karma, purify the being, and allow it to approach the Supreme Person.
Krishna, God, the Supreme Person says: It is the desires and thoughts at the moment of death that determine what your next existence will be.
As spiritual souls, we are always immortal because of our intrinsic nature, but we change bodies. This process is creative in the sense that we create our own body, or our next body, according to our desire. If we cultivate the mentality of a dog within ourselves, we will obtain a dog's body in our next life. If we are passionate about surfing, we will create within ourselves the mentality of beings who love living in the water. Therefore, if we think about this at the time of death, we will obtain an aquatic body in our next life. Naturally, at the time of death, if we think about something specific, nature will give us a corresponding body through specific parents, whether human or animal. This is an irresistible process.
No being, whether on Earth or among the celestial beings on the higher planetary systems, is free from the influence of the three attributes and modes of influence arising from material nature: goodness, passion, and ignorance.
The soul acquires a particular body according to its status regarding the three modes of material nature: goodness, passion, and ignorance.
If its appetite is insatiable and it eats indiscriminately, the soul will assume the body of a pig. If it desires to kill and feed on flesh and blood, it will take the body of a tiger. But if it desires to eat food offered to God, it will obtain the body of a sage. Different bodies are thus granted to us according to our desires.
Similarly, if you develop the mentality of a servant of God, you will return to Krishna, God, the Supreme Personality, in His absolute kingdom. The purpose of life is to attain spiritual realization and to re-establish our now-forgotten relationship with God.