AFFLICTION

"I have refined you in the furnace of suffering." Isaiah 48:10

One of the reasons why God uses afflictions, is to prevent Christians from backsliding. In times of prosperity . . .
  pride is apt to rise and swell;
  carnal security blinds their eyes;
  the love of riches increases;
  spiritual affections are feeble;
  eternal things are viewed as far off, and concealed by a thick mist.
These circumstances are, indeed, the common precursors of backsliding.

But to prevent this evil, and to stir up the benumbed feelings of piety--the believer is put into the furnace! At first he finds it hard to submit, and is like a wild bull in a net. His pride and his love of carnal ease, resist the hand that smites him; but severe pain awakes him from his spiritual sleep. He then finds himself in the hands of his heavenly Father--and sees that nothing can be gained by murmuring or rebelling. His sins rise up to view, and he is convinced of the justice of the divine dispensations. His hard heart begins to yield, and he is stirred up to cry mightily to God for helping grace. Although he wishes and prays for deliverance from the pressure of affliction--yet he is more solicitous that the affliction should be rendered effectual . . .
  to subdue his pride,
  to wean him from the love of the world, and
  to give perfect exercise to patience and resignation
--than that it should be removed. He knows that the furnace is the place for purification. He hopes and prays that his dross may be consumed, and that he may come forth as gold which has passed seven times through the refiner's fire!
(Archibald Alexander, "Thoughts on Religious Experience" 1844)