Prophet Ayyub was once very wealthy — land, livestock, gardens, healthy children. Allah wanted to test whether his worship was sincere because of blessings, or because of Allah Himself.
First, all his wealth was lost. Ayyub gave thanks: "Allah gives, Allah takes. Praised be Allah's name."
Second, all his children passed away. Ayyub wept but said: "Innaa lillaahi wa innaa ilaihi raji'uun." He didn't blame Allah.
Third, Ayyub's body was struck with severe skin disease. For 18 years he suffered. Only his loyal wife cared for him. People distanced themselves. But every day Ayyub kept praying to Allah.
Finally Ayyub said very politely to Allah: "(My Lord), affliction has touched me, and You are the Most Merciful of those who show mercy." (Al-Anbiya: 83) — notice: Ayyub didn't demand, only described his state.
Allah commanded Ayyub to strike the ground with his foot. A spring burst forth. Allah told him to drink and bathe in that water. His illness disappeared. Allah returned his wealth doubled. Allah also replaced his children.
For children: the most patient person isn't one who feels no pain — but one who feels pain and still says "alhamdulillah."