As Allah gave people a lot of blessings because of His mercy, He gave people imperfections and inadequacies too so that they should desire Paradise. Sincere Muslims consider these inadequaces and imperfections as a blessing that Allah bestowed upon them. They thank Allah for them, and pray to enter His Paradise.
Diseases are examinations so that humans should desire Paradise. They should think about Allah’s blessings, value their health and thank Him; and thus, they should understand their inedaquacies and obey Him.
In their daily lives, humans tend to see many blessings conferred on them as a part of natural life; humans should remember it is Allah Who gave everything that they have as a mercy from His presence. For example, many people do not think about important blessings such as: how they walk without a problem, how they stand on their feet when they wake up every morning. If any problem might occur with their feet , it would affect their entire daily lives.
A foot that is unable to step and to feel painful , for a human, causes them to understand how much of a blessing it is to take steps a thousands times within a day. Muslims consider all matters like this, big or small, as a means to be near Allah. They will thank Allah, remembering how Allah gave them an immense benefit by granting them health. They know that Allah is the One Who gives and takes thier disease and they will expect the cure from Allah.
Every time they feel pain, they remember Allah, and keep their hearts with Him.
He Who created me and guides me;
He Who gives me food and gives me drink;
and when I am ill, it is He Who heals me;
He Who will cause my death, then give me life;
He Who I sincerely hope will forgive my mistakes on the Day of Reckoning.
My Lord, give me right judgment and unite me with the righteous;
and make me highly esteemed among the later peoples;
and make me one of the inheritors of the Garden of Delight (Surat ash-Shu‘ara, 78-85)