What is the warning "Al Tefen El Aven"?
Rashi: Do not judge, and say that Hashem should have judged you with poverty 1 [in place of your afflictions]. One who was always rich, and people honored him, [and now he is poor], if he wants to buy something, but lacks money, he returns sad to his house. This is from Tanchuma. Also the Agados and Gemara (Bava Basra 116a) say that poverty is worse than Iyov's afflictions 2 .
Malbim: When you had serenity, you prayed to be guarded from sin and heresy. How will He accept your request to judge your virtue, now that amidst poverty, you chose sin, and to be like nations and deny Hashgachah. You failed the test of poverty! The Satan was right; your virtue was not pure, rather, amidst 'Kofer' that Hashem gave to you.
Rashi: Do not say that now, Iyov was poor. We find that he lost his animals, but not his gold and silver! And even if he lost his gold and silver, it is better to be sick and poor, than intact and going in the market without anything.
Does an Oni curse his day, and want to die? Why were his friends silent for seven days when they saw him? Perhaps poverty is harsher, but it is common, so people do react to it so much. (PF)


