If someone wrote Sonnet 30 to me, I would feel very good indeed. Most of the poem is about the speaker’s regrets. The language is old fashioned, but if you look at phrases like “I sigh with old woes,” and “my dear time’s waste,” you can see that the poet’s looking back at the past with regret. For the first two stanzas the poet moans about one thing after another, but in the last two lines of the third stanza, there’s a turn. Addressing the recipient of the poem as a “dear friend,” the speaker of the poem proclaims “all losses are restored and sorrows end” when he thinks of his friend. The memories of this friend more than make up for all of the regrets.
Does it matter whether the recipient of the letter is a man or a woman? This is a love letter to a friend, rather than a sexual partner, so I don't think it matters much.