In despair, man rises above the fetters of this world. This world, i intuit, has an element of forgetfulness to it. Its a trap of illusion that deludes many. The chains of senses imprison us. Hunger, passion, thirst, lust, caprices, etc., can reduce us to an animal. But in despair all of this is cracked open. In fact, all of the chains melt away. Forgetfulness of imminent, inevitable, unavoidable death vanishes. Delusion of independence of man is seriously challenged. Naive belief in absolute efficacy of our efforts, and the causes, falters.
Interestingly, while the whole day is spent in the agony of despair, it is punctuated by very brief moments of unjustifiable euphoria. After it dissipates, horizon looks gloomier.
Despair only teaches us to lean on the Absolute. Tribulation is seen by spiritual and religious masters as a blessing in disguise that connects us to our Beloved, with whom depths of our souls so want to reunite. As one's animalistic desires dissolve - of eating, drinking and taking pleasures of various kinds - one sincerely and actively invokes Allah's name. And after tribulation ends, hearts solidify and everything becomes history.
This isn't the sum-total of something one might experience from despair. A skeptical mind, (either) brainwashed by modernism and/or thanks to the whispers of Satan, can view things differently, although not objectively. He can say in his very despair that i'm invoking God because i need him. Hence, my mind has invented him as a support. He doesn't necessarily exist. (Curiously this has nothing to with the realm of pure intellect, rather emotion. For if pure intellect [not separated from heart] had been operating, there won't have been any despair in the first place.)
Here, firstly, the existence of God has nothing to do with this inversion or error-ridden whisper by torch-bearer of falsehood. The fact that one yearns to lean on the Absolute and find solace in it is what metaphysicians point to as 'truth within us'. 'We know truth because we are truth,' says Frithjof Schuon. Secondly, this has to do with skepticism, which doubts everything. In its limitation lies its singular cure:
"Ibn-e-Sina talks of a hanging man, who is hung in the middle of space. His feet don't touch anything; his legs don't touch anything. He doesn't know where he is. [Thus] he can doubt the existence of earth, he can doubt the existence of air - there is nothing he cannot doubt! The one [and only] thing he cannot doubt is himself that is doubting everything.""'I think therefore God is.' Not that 'I think therefore I am'." - Seyyed Hossein Nasr, In the Beginning was Consciousness, The Dudleian Lecture delivered at Harvard Divinity School.