This is a very serious illness, for which the Prophet, sallallahu 'alayhi wa sallam (may Allah's peace and blessing be upon him), has given the cure. He, sallallahu 'alayhi wa sallam, admonished us, in terms of worldly things to always look to those beneath us, for this will keep us thankful. Allah says about the Prophet, sallallahu 'alayhi wa sallam, that in him we have the best of examples. In terms of showing us how to be thankful to Allah, subhanahu wa ta'ala, he is as Allah says. It is narrated by al-Mughira that the Prophet, sallallahu 'alayhi wa sallam, used to stand in the salah (prayer) or performed salah until both his feet or legs swelled. He was asked why (he offered such an unbearable salah) he said, "Should I not be a thankful slave?" [Al-Bukhari]