Uki o nao mukashi no yue to omowazu wa ika ni kono yo o uramihatemashi - Shin Kokin Wakashu(English Translation & Meaning)

憂きをなを昔のゆへと思はずは
いかにこの世を恨みはてまし

Roma-ji: Uki o nao mukashi no yue to omowazu wa ika ni kono yo o uramihatemashi
English Translation: These sorrows, still, if
as due to a former life
I did not think them,
how bitterly this world
I would have come to resent!
Meaning: Had I not thought my sorrows the fruit of a former life, how utterly I would have resented this world!
Commentary: Book Twenty Buddhist Poems 1965

Headnote: "When poems on the Ten Suchnesses were commissioned at the house of the Lay Monk and Former Regent, on 'Such a Retribution.'"
This is the first poem in the sequence of poems by various poets on scriptural phrases and Buddhist observances. Had the poet not thought her sorrows the retribution of a former life, how bitterly would she have resented this world! According to the headnote, it was composed on "Such a Retribution" when poems on the Ten Suchnesses were commissioned at the house of Kujō Kanezane.
By accepting the pains of this world as retribution for causes in a former life, she seeks to calm her resentment of the world, finding salvation in the Buddha's teaching.
The author, "Nijō-in no Sanuki," was a daughter of Minamoto no Yorimasa and a lady-in-waiting and poet who served Emperor Nijō. She later served Ninshi, known as Gishūmon-in, empress of Emperor Go-Toba.
The Ten Suchnesses, taught in the Expedient Means chapter of the Lotus Sutra, are ten categories showing the nature of all things: such an appearance, such a nature, such an entity, such a power, such an influence, such a cause, such a condition, such an effect, such a retribution, and such a consistency from beginning to end. "Such a retribution" is the recompense received later as a result of causes and conditions.

The first line, "uki o nao," means "my sorrows, still," pointing to the suffering received in this world.
The second line, "mukashi no yue to," means "as due to causes in a former life," showing the topic "such a retribution."
The third line, "omowazu wa," means "if I did not think so," a hypothetical condition formed by the negative "zu" with "wa."
The fourth line, "ika ni kono yo o," means "how much this world," suggesting the depth of resentment.
The last line, "uramihatemashi," closes with the counterfactual "mashi": "I would have resented it to the end." Answering the hypothesis of the third line, it shows that knowing it as retribution barely calms her resentment.
Author: Nijoin no Sanuki
Source: Shin Kokin Wakashu
Prev Poem: Hana no moto tsuyu no nasake wa hodo mo araji ei na susume so haru no yamakaze
Next Poem: Watasubeki kazu mo kagiranu hashibashira ika ni tatekeru chikai naruran