Here is reprint on suffering from the sayings of the saints that was originally posted at Enlarging the Heart. I recommend this blog site. It is a wonderful treasury of the sayings of saints.
Just as sick people need surgery and cautery to recover the health they have lost, so we need trials, and toils of repentance, and fear of death and punishment, so that we may regain our former health of soul and shake off the sickness which our folly has induced.
The more the Physician of our souls bestows upon us voluntary and involuntary suffering, the more we should thank Him for His compassion and accept the suffering joyfully.
For it is to help us that He increases our tribulation, both through the sufferings we willingly embrace in our repentance and through the trials and punishments not subject to our will.
In this way, if we voluntarily accept affliction, we will be freed from our sickness and from the punishments to come, and perhaps even from present punishments as well.
Even if we are not grateful, our Physician in His grace will still heal us, although by means of chastisement and manifold trials. But if we cling to our disease and persist in it, we will deservedly bring upon ourselves age-long punishment.
[…] We do not all receive blessings in the same way. Some, on receiving the fire of the Lord, that is, His word, put it into practice and so become softer of heart, like wax, while others through laziness become harder than clay and altogether stone-like.
And no one compels us to receive these blessings in different ways. It is as with the sun whose rays illumine all the world: the person who wants to see it can do so, while the person who does not want to see it is not forced to, so that he alone is to blame for his lightless condition.
For God made both the sun and man’s eyes, but how man uses them depends on himself. Similarly, then, God irradiates knowledge to all and at the same time He gives us faith as an eye through which we can perceive it.
[…] Greater practice is rewarded by greater knowledge; and from the understanding thus acquired we gain control of the passions and learn how to endure our sufferings patiently.
Sufferings produce devotion to God and a recognition of His gifts and our faults. These give birth to gratitude, and gratitude inculcates the fear of God which leads us to the keeping of the commandments, to inward grief, gentleness and humility.
These three virtues produce discrimination, which…makes it possible for the intellect…to foresee coming faults and to forestall them through its experience and recollection of what has happened in the past. In this way it can protect itself against stealthy attacks.
Peter of Damascus (?12th Century): A Treasury of Divine Knowledge Text from G.E.H. Palmer, Philip Sherrard, and Kallistos Ware (trans. and eds.) The Philokalia: The Complete Text, vol. 4 (Faber & Faber, London & Boston: 1979ff), pp. 77-78.