"Earthly life—this brief period—is given to man by the mercy of the Creator in order that man may use it for his salvation, that is, for the restoration of himself from death to life…" St. Ignatius Brianchaninov (The Arena).
Father Alexey Young
But if we are sons, we are heirs also: heirs indeed of God and joint heirs with Christ, provided, however, we suffer with Him that we may also be glorified with Him (Rom. 8:17) Therefore, we must "..look upon everything in this world as upon a fleeting shadow and cling with our heart to nothing of it...for we look not at the things which are seen, but at the things which are not seen; for the things which are seen are temporal, but the things which are not seen are eternal" (St. John of Kronstadt, Spiritual Counsels).
For Orthodox Christians, the center of our life is not here, but there, in the eternal world.
How long we live, what disease or illness accompanies our death—such things are not the proper concern of Orthodox Christians. Although we sing "many years" for one another at Namesdays and other celebrations, this is only because the Church in her wisdom knows that we indeed need "many years" to repent of our sins and be converted, not because a long life has any value in itself. God is not interested in how old we are when we come before His Judgment, but whether we have repented.
He (God) is not concerned about whether we died of a heart attack or cancer, but whether our soul is in a state of health.
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" (Sts. Barsanuphius and John, Philokalia).