[Matt Q]

If "again" works for you, then how about?:

Now the soul frets anxiously again

"Fret" gives you repine -- in English at least. Though from your list of synonyms earlier, maybe "yearns" would fit it better? The line then seems closer to the crib. The repining is clear, which I don't think it is in the current version, and the recurrence (the "again") is now mentioned.

What the current line says seems unclear to me, which I guess is makes it seem awkwardly phrased and hence rhyme-driven. Either a pang -- a sudden pain or painful emotion -- coincides with the arrival of anxiety, or the anxiety arrives in the form of a pang. I'm more inclined to read the latter, because otherwise no candidate for the pang is suggested, and normally one is. Read this way, though, the repining is lost. If read as the former, I'm guessing at what it's a pang of. Several of usual suspects -- loss, sorrow, longing -- would work with "repine", but others like guilt, jealousy, hunger etc. don't.

-Matt