Vilna Gaon (19) #1: I do not anticipate good for the rest of my life. Hashem, Midas ha'Rachamim, afflicted me. If Midas ha'Din afflicts someone, there is hope that the anger will pass and He will have mercy on him again, but not when Midas ha'Rachamim punishes. This is like a merciful father beating his son who killed his brother. He does not beat him amidst cruelty, rather, amidst mercy - he is pained over the loss of his beloved son! Hashem punished Na'ami for not having mercy on the poor - "v'Hayah Ki Yitz'ak Elai v'Shamati Ki Chanun Ani" (Shemos 22:26). Punishment due to Chaninah is great.

Vilna Gaon (19) #2: "Ach Tov va'Chesed Yirdefuni Kol Yemei Chayai" (Tehilim 23:6) - when a man constantly has good, this is Redifah (pursuit to destroy him), for it causes him to rebel against his Maker and diminishes his trust in Him - "va'Yishman Yeshurun va'Yiv'at" (Devarim 32:15). It is better to have some afflictions in this world; they bring one close to Avodas Hashem! "Tzaros Levavi Hirchivu" (Tehilim 25:17) - they widened my heart in His Avodah. "Mi'Metzukosai Hotzi'eni" (ibid.) - Tzar is external [affliction], and Matzok is internal - "b'Matzor uv'Matzok Asher Yatzik Lecha Oyivcha b'Chol She'arecha" (Devarim 28:55). It does not say Asher Yatzur Lecha, for Matzor is outside the city, and Matzok is inside. The external Tzaros that surround me, to block me [from Avodas Hashem, and force me] to do like their desires - this widened my heart in His Avodah. However, from Metzukosai - what pertains to inside the heart - save me. You are astounded, "ha'Zos Na'ami" (19) - she used to be called based on good that she had - rather, call me Marah. My initial good decreased my Emunah. I descended from Eretz Yisrael to Chutz la'Aretz. When I was surrounded by afflictions, I merited that Hashem return me to here.

Malbim: If one had awesome wealth like Achashverosh, and lost it, and only 1000 gold coins remained, we say that he became poor. If we ignore his previous wealth, he is now rich. If he is left without any money or food, he is poor even without considering his previous wealth. When people saw Na'ami and her daughter-in-law without any servants, they knew that she lost her prior wealth, but they thought that she still had gold and ornaments that a commoner would rejoice to have such wealth. Their astonishment was "ha'Zos Na'ami" (19), due to her prior wealth. She informed them that now she is intrinsically Marah, even without considering her descent [from 'Na'ami']; she has nothing. Her daughter-in-law needed to gather Matanos Aniyim!