"I keep coming back to you in my head, but you couldn't know that, and I have no carbons"

In this quote, Adrienne Rich expresses the concept of continuously thinking about somebody, even though they might not understand it. The phrase "returning to you in my head" recommends that this individual occupies a significant space in the speaker's thoughts. Nevertheless, making use of "you could not know that" implies that the speaker is not able to communicate these ideas to the person they are thinking about. The phrase "I have no carbons" even more highlights this concept of being not able to reveal oneself, as carbons are used to make copies of composed files. In general, this quote conveys a sense of yearning and frustration in the speaker's unmentioned sensations towards this individual.