Sonnet 30 is at the center of a sequence of sonnets dealing with the narrator's growing attachment to the fair lord and the narrator's paralyzing inability to function without him. The sonnet begins with the image of the poet drifting off into the "remembrance of things past" - painful memories, we soon learn, that the poet has already lamented but now must lament anew. The fair lord enters the scene only in the sonnet's closing couplet, where he is presented as a panacea for the poet's emotional distress.
Closely mirroring the message of sonnet 29, here Shakespeare cleverly heightens the expression of his overwhelming anxiety by belaboring the theme of emotional dependence. Whereas in sonnet 29 he quits his whining after the second quatrain, in sonnet 30 three full quatrains are devoted to the narrator's grief, suggesting that his dependence on the fair lord is increasing. Meanwhile sonnet 30's closing couplet reiterates lines 9-14 of sonnet 29 in compact form, emphasizing that the fair lord is a necessity for the poet's emotional well-being: the fair lord is the only thing that can bring the poet happiness.
This pinnacle of the poet's plaintive state is beautifully conveyed through an artful use of repetition and internal rhyme. Beyond the obvious alliteration of "sessions of sweet silent thought," note the "-nce" assonance of "remembrance" and "grievances," to which may be added "since" and "cancell'd"; the correspondence of "sigh," "sought," and "sight"; and the rhyme in "foregone," "fore-bemoaned," "before," and "restored." It is as though the poet wishes to hammer in his hardship with the repetitive droning of his troubled soul.
Beyond its poetics, sonnet 30 also provides some prime examples of the poet's recurring tendency to describe his relationship with the fair lord in financial terms. The opening lines of the sonnet remind us of being called to court (cf. "court sessions" and "summon a witness"). This is followed by a slew of money-related terms, including "expense," "grievances," "account," "paid," and "losses." The phrase "tell o'er" in line 10 is an accounting expression (cf. the modern bank teller) and conjures up an image of the narrator reconciling a balance sheet of his former woes and likening them to debts that he can never pay off in full. The only cure for his financial hardship is the fair lord's patronage - perhaps something to be taken literally, suggesting that the fair lord is in fact the poet's real-world financial benefactor.