The thief (Satan) comes only in order to steal and kill and destroy. I (Jesus) came that they may have and enjoy life, and have it in abundance (to the full, till it overflows).

Jesus loosed/freed/released a Woman whom Satan had bound for 18 years:

Luke 13:11-12 (AMP)  And there was a woman there who for eighteen years had had an infirmity caused by a spirit (a demon of sickness). She was bent completely forward and utterly unable to straighten herself up or to look upward.  And when Jesus saw her, He called [her to Him] and said to her, Woman, you are released from your infirmity! 

It was never God's intent that sickness "teach us something."  The ONLY thing God uses to perfect us is The Bible (The Word):

2 Timothy 3:16-17 (NIV)
All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, so that the man of God may be thoroughly equipped for every good work. 

The Word is what heals us:

Psalm 107:20 (NIV)   He sent forth his word and healed them; he rescued them from the grave.