SubhaanAllah. Illness is yet another means whereby the imaan of the believers is tried. How easy it is to rebel and lose patience in a time of pain and distress. Yet it is only in the fire that the iron is molded to perfection. Illness is a means to the expiation of sins for us because through it we show Sabr and shukr - we forego our pain, our difficulty, our inadequacy to do our daily jobs, etc. for the sake of humbly submitting to Allah. In doing so, we elevate in our hearts the significance of His decree and lower that of our own desires.
May Allah ta'ala keep us good and healthy; may He make any illnesses we have a means to earning His rahmah and forgiveness for our shortcomings.