Yo no tsune no koto to mo sara ni omōezu hajimete mono o omou mi nareba - Izumi Shikibu Nikki(English Translation & Meaning)

よの常の事ともさらにおもほえす
初て物をおもふみなれは

Roma-ji: Yo no tsune no koto to mo sara ni omōezu hajimete mono o omou mi nareba
English Translation: As a common thing,
as the way of the world, never
could I think of it;
for I am one who now, at last,
knows what it is to love
Meaning: I cannot think of it at all as something ordinary in this world, for this is the first time I have known such longing.
Commentary: 3 The First Night Together

On receiving her reply, the prince unexpectedly resolved to visit her in secret and made ready from midday. He summoned the man of the Right Palace Guards who usually carried his letters and told him they were going out; the man understood and attended him. The prince came in a humble carriage and had his arrival announced. Izumi Shikibu felt it was most awkward, but she could not claim to be away, and having answered him that very afternoon, she thought it unkind to send him back, so, meaning only to talk, she set out a round cushion at the west double door and let him in. The prince was every bit as graceful as people said. As they talked, the moon rose and grew very bright. "Being an old-fashioned, retiring sort," he said, "I am not used to sitting so near the edge, and I feel exposed. Let me sit where you are. I will not behave like the men you have known." She answered lightly, "How strange. I meant only to talk with you tonight. What men I have known?" Meanwhile the night grew steadily later.
The woman is Izumi Shikibu, daughter of Ōe no Masamune and, as the wife of Tachibana no Michisada, Governor of Izumi, mother of Koshikibu no Naishi. The prince is Prince Atsumichi, fourth son of Emperor Reizei. The man of the Right Palace Guards was the prince's close attendant who carried his letters and accompanied him on his outings; the title refers to a third-rank officer of the Right Inner Palace Guards.
After their talk through the blinds, the prince quietly slipped inside and the two exchanged vows. When the prince, having gone home at dawn, sent his morning-after poem "Koi to ieba yo no tsune no to ya omouran kesa no kokoro wa tagui dani nashi," Izumi Shikibu sent back this poem.
Even after answering, she wondered at her own strange fate and what had come over her, and grieved, remembering how much the late prince had once said to her. When the usual page boy came, she hoped for a letter from the prince, but there was none, and she reproached herself for feeling hurt, as though she were some woman given to love.

The first three lines mean "I cannot think of it at all as an ordinary thing," taking up the prince's "ordinary" word for word, with a construction of complete negation.
The lower verses mean "because I am one who for the first time knows longing," giving her reason. By declaring this the "first time," Izumi Shikibu, known as a woman of many loves, shows a depth of feeling equal to his "nothing to compare," meeting his words on the same level.
Author: Izumi Shikibu
Source: Izumi Shikibu Nikki
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