“Past reason” takes on a different meaning here: it is not the reason that he ignored initially, but the reasoning that allowed him to fulfill his desire and ignore his internal inhibitions. The repetition of the phrase “past reason” in these two lines signifies his internal struggle: both the reason to abstain and the reason to indulge exist within him.
In this line, the speaker leads with the idea of “enjoyment” rather than shame. Like the last line of the poem, the feelings presented follow the emotional arc of the speaker rather than constructing a logical argument. This sequence of words represents the speaker’s lack of logic and loss of control.
The notion of lust as “perjured” suggests that lust causes one to commit perjury—to lie and be unfaithful. Some scholars believe that the woman in Sonnet 129 is a prostitute, which reinforces the idea of the speaker being unfaithful.
