Imaam Ibnul Jawzi (rahimahullaah) said:
Indeed, I see that when the majority of the people are afflicted with illness, they would sometimes preoccupy themselves with (feelings) of anguish and complain, and sometimes they would preoccupy themselves with medication (i.e. a type of preoccupation that diverts them from obligations). So preoccupation with the severity (of the illness) diverts them from the beneficial commandments, performance of good deeds or preparation for death. And how many have sins which they have not repented from, an unfulfilled trust, a debt, Zakat (to pay) or a misdeed related to a responsibility of theirs! However, their sadness (is focused on the thought of having to) part with the worldly life. Indeed, this is common amongst the majority of the creation and we seek Allaah’s protection from being forsaken. Therefore, it is incumbent upon a cautious person that he (or she) is prepared when in a state of good health before a state of poor health.
[Source: Ath-Thabaat Indal Mamaat: page: 31 Abridged & slightly paraphrased]