Write, for example, "The night is starry and the stars are blue and shiver in the distance."
It's not entirely clear just how much of this poem is supposed to be an example of the "saddest lines," since Neruda deliberately leaves that ambiguous. However, there's no ambiguity here: this stanza is clearly intended as an example of sad lines. Interestingly, though, "The night is starry and the stars are blue and shiver in the distance" is not what most people would consider an extremely sad line. This line is moody, hinting at desolation and loneliness, but it is hardly tragic or heartwrenching. It becomes apparent that, while the speaker feels so sad that he wants to or feels capable of writing very sad lines, he's actually not willing or able to do so, because his own sadness is so raw, draining, and confusing. In the case of the speaker, emotion seems to dull rather than sharpen poetic sensibility, making the understatedness of this line, strangely, all the sadder.
To hear the immense night, still more immense without her.
And the verse falls to the soul like dew to the pasture.
This two-line stanza offers a great deal of information about the speaker's emotional, and artistic, state. In the first of the two lines, the speaker compares his perception of two identical nights. His setting is unchanged, but, because his lover is gone, the setting feels different—vaster, lonelier, and more alienating. In other words, nature's consistency makes his changing situation feel all the more dramatic and bewildering. At the same time, his dramatic, bewildering situation actually makes the natural world feel different when it hasn't changed at all.
In the second of these two lines, meanwhile, the speaker compares himself, or at least his soul, to a pasture, so that through metaphor he actually becomes part of that unfeeling, passive natural landscape. Poetry, within this metaphor, simply happens to him without conscious effort or activity. This is one reason why his assertion that he can "write the saddest lines" doesn't entirely ring true. The speaker is confused and tired, and isn't able to manipulate language. Instead, language arises involuntarily from him, imperfect and unexpected.
Another's. She will be another's. As she was before my kisses.
Her voice, her bright body. Her infinite eyes.
In these lines, the speaker appears to try rationalizing his feelings by creating a mental separation between himself and his lover. Rather than think of his lover through the lens of their shared time together, he thinks of her as a separate being whose life will take shape in his absence. He reminds himself that she will be with somebody else, and he tries to remember and describe different parts of her body—not in terms of his interactions with that body, but in terms of its own discrete, separate existence. Yet the use of caesura, fragmented sentences, and short, end-stopped lines show that the speaker is struggling and stumbling. Even as he attempts this particular variety of rationalization, he is unable to speak clearly and fluently, revealing that it feels counterintuitive and upsetting.
