Whereas Sonnet 132 makes the mistress into a chaste beauty, Sonnet 133 maligns her for seducing the poet's friend, the young man: "Beshrew that heart that makes my heart to groan / For that deep wound it gives my friend and me." Whether or not this "deep wound" is caused by the woman's having had a sexual affair with the youth is unclear. The "slave to slavery" phrase in line 4 may be more about jealousy than about lust, for the poet seems enamored here with both the woman and the young man.
The woman's pitiful eyes contrast with her cruel and flirtatious heart. Cynically, the "mourning eyes" of Sonnet 132 have become "cruel" eyes that torment the poet. Attempting to protect the youth from the woman's advances, the poet argues that because the young man resides in the poet's own heart, the woman can have the young man only by having the poet, whose heart will guard the heart of the youth from any cruelty the woman may do him. However, the sonnet's last two lines make clear that the poet knows that the woman will be cruel not only to him but to the young man.
beshrew a mild curse.