The daughter helps to destroy the mother

(Thomas Watson)

"And we know that all things work together for good
 to those who love God, to those who are the called
 according to His purpose." Romans 8:28

Afflictions work for good to the godly, as they are
destructive to sin. Sin is the 'mother', affliction is
the 'daughter'; the daughter helps to destroy
the mother.

Sin is like the tree which breeds the worm; and
affliction is like the worm which eats the tree.

There is much corruption in the best heart; affliction
does by degrees work it out, as the fire works out the
dross from the gold, "The Lord did this to purge away
his sin." (Isaiah 37:9)

What if we have more of the rough file—if we have
less rust! Afflictions carry away nothing but the dross
of sin. Afflictions are the medicines which God uses
to cure our spiritual diseases. Afflictions cure . . .
  the swelling of pride,
  the fever of lust,
  the cancer of covetousness.