The speaker never says "I am in love". Instead, the poem opens by speaking to a breath: "Oh Sigh!" The sigh is a "herald of the breast," a messenger that runs ahead to announce what the heart would rather keep private. The verb "steal'st" makes it a sneaky messenger, slipping out unbidden. At first the feeling is general, "the lover's fears, the lover's pangs," as if the speaker were describing a type of person. Only in line six does it turn personal, with "my fading cheek." The poem begins as an observation about lovers and becomes a confession.
The octave follows the Petrarchan pattern, with two quatrains rhymed ABBA ABBA, and the rhymes do real work. One sound, "-est," runs through *breast*, *rest*, *confest* and *prest*. These four words cover the poem's whole predicament: the body that holds the feeling, the sleep it costs, the secret that leaks out, and the weight pressing down. The other rhyme group, *tell*, *swell*, *dwell*, *bell*, is softer and more liquid, much like the tears it accompanies. Line 4, "Cheating the day of joy, the night of rest!", is balanced and neat. Love robs both halves of the twenty-four hours, so there is nowhere to hide from it.
The tears get the poem's most interesting paradox. They are "lucid" and "with eloquence confest," so they speak more clearly than words could. Yet they "unheeded dwell," and no one reads them. The speaker has a perfectly expressive body and no audience for it. The simile that follows deepens the sadness. The tears are "dew-drops on the flowret's bell," and the speaker is the flower, forced "by ruthless tempests to the green-sod prest." Dew normally suggests morning freshness, but here it clings to a storm-battered plant. "Meek" tells us the flower does not protest. The soft sounds of "dew-drops" and "flowret's bell" set off the harsher "ruthless tempests," and "sod" may carry a faint hint of the grave, though that is an inference from the image.
At line 9 the volta arrives, and the poem changes from describing to commanding. "Fond sigh be hush'd! congeal, O! slighted tear!" Here "fond" probably means foolish as well as loving, which is a harsh thing to say to one's own feelings. "Congeal" is a striking word to choose. It turns the earlier flowing tears into something frozen and still, the opposite of "crystal streams." Line 10, "Thy feeble pow'rs the busy Fates control!", can be read as an exclamation that the Fates overrule the sigh's weak powers, or as a flat statement that the sigh cannot control anything. Either way, the speaker has decided that the body's language is useless against forces that care nothing for it.
The speaker's fallback is a bleak bargain. If the tears must return, "Let them, like Lethe's, oblivion roll." Lethe is the river of forgetfulness in classical myth. Tears that once confessed love are now asked to wash it away, and weeping becomes a means of erasing the very feeling that caused it.
The ending refuses easy comfort. The sestet alternates its rhymes (*tear*, *control*, *appear*, *roll*, *near*, *soul*), and the last two lines, *near* and *soul*, do not rhyme with each other, so there is no tidy closing couplet. The poem ends on a paradox: "Love the tyrant plays, when hope is near, / And she who flies the lover, chains the soul!" "Plays" suggests both acting a part and toying with a victim, and the tyranny strikes just as hope approaches. Then comes the cruelest antithesis. The beloved "flies," meaning flees, and yet "chains," so the one who runs away is the one who holds the speaker captive. It also matters that the poem ends on "soul," having begun with "breast." It moves from the physical sign to the thing the sign points to, which cannot be silenced.
The poem is significant because it shows feeling as something the body does against its owner's will. Its vocabulary (*thou*, *flowret*, *Fates*, *Lethe*) belongs to an elevated, traditional style, but the situation is familiar to anyone who has failed to hide how they feel. Its title, "Sonnet XXXVIII," suggests it belongs to a longer sequence, though it stands well alone. The speaker orders the sigh to be quiet, yet the poem's piled-up "Oh"s and exclamation marks are themselves a series of sighs, so the attempt at silence defeats itself.