What is despair of Allah's mercy? What are its forms? Is pessimism, by expecting a calamity without cause, an act of disbelief (kufr)? And is expecting not to get good grades due to not studying well considered pessimism and despair of Allah's mercy?

Despairing of Allah's mercy is a sin that can escalate to disbelief (kufr) if it leads to a complete denial of the vastness of Allah's mercy and the absence of all hope. However, if the root of hope remains, it is considered a major sin.

Thus, despair that is considered disbelief is the complete absence of hope in Allah's mercy, whereas despair that is a major sin involves the existence of a root of hope alongside the dominance of despair.

The difference between despair as disbelief and as a major sin is as follows: Despair is disbelief if hope in Allah is completely absent. However, if there is despair alongside the existence of hope, it is a sin, and its perpetrator does not exit the fold of Islam.

Despair can escalate to utter hopelessness (qunut), which is the firm conviction that mercy will not be attained, or having ill thoughts of Allah by expecting an increase in torment.

It has been forbidden to despair of provision, to despair due to poverty or calamities, and to despair of the forgiveness of sins, for Allah forgives all sins.

Pessimism differs from despair. Expecting a calamity based on the indications of events and circumstances is not a form of pessimism or despair; rather, it is a matter of wisdom and intellect, and it does not contradict hope in Allah's mercy.