God did not come into the world to eradicate suffering. He did not come even to explain it. God came into the world to fill human suffering with His presence. Paul Claudel
If the occasion demands it, a wise man will readily accept bodily infirmity and even offer his whole body up to death for the sake of Christ. This same man is not affected in spirit or broken with bodily pain if his health fails him. He is consoled by his struggle for perfection in virtues. St. Ambrose of Milan (Exegetical Works)
Without Divine Revelation man cannot understand the origin and cause of pain, nor its purpose. Many people, not having help in understanding, are haunted by fear of pain, terrified at the thought of a lingering illness, and quick to seek medical relief because they believe illness is only the result of “chance” (i.e. genetics, DNA)
Monasticism – martyrdom - suffering an incurable affliction - are all the same thing spiritually. Ask God to give, not merely guidance or help, but martyrdom - suffering a path where you can make a supreme effort…‘get-involved’ become on fire to serve God.'” He will not abandon you, and through the sickness that afflicts the body, the health of your soul and spirit will increase - and the result will be true joy, and a contentedness, not of this world, will become yours.
Therefore, "we should not dread any human ill, save sin alone; neither poverty, nor disease, nor insult, nor malicious treatment, nor humiliation, nor death" (St. John Chrysostom, On the Statues), for these "ills" are only words; they have no reality for those who are living for the Kingdom of Heaven.
The only real "calamity" in this life is offending God.
If we have this basic understanding of the purpose of life, then the spiritual meaning of bodily infirmity can be opened for us. For every sin is a renewal of the sin of the first-created ones, a willful turning away from God towards self. In this way we set ourselves in the place of God, actually worshipping self instead of the Creator. In this way the suffering of illness serves the same purpose today as it did in the beginning: for this reason it is a sign of God's mercy and love. As the Holy Fathers say to those who are ill:
God has not forgotten you. He cares for you, He is with you."
+ Glory to God for All Things +
Sts. Barsanuphius and John, Philokalia