To the best of my ability (and based upon the way this poem speaks to me personally), the confessional nature of Carolyn's Kizer's poem seems quite strong in "Night Sounds." Often when we hear the word "confession," we think of someone referring to something criminal; confessional may make some readers think of "confession" in church, still accompanied with the sense that what is being spoken of is about is of dire importance. My sense of this poem is not that the speaker has done something wrong—unless it be perceived that way by her ex-lover. The nature of the speaker's confession is simply that she has not been able to move on: she still misses the man who is no longer with her: and her loss is not for one night, but permanent when she says, "Living alone now..."
We can assume it is a man she writes about—with the phrase "heavy, impassive back." We may also assume that the relationship was never good, perhaps was really one-sided: the speaker had to "coax" this man to hold her; he was never "able to lie quite peacefully at my side..." and "Always withholding something." The speaker goes on to describe what it was like as he tried to take his leave of her, believing she was asleep:
Awake before morning, restless and uneasy,
Trying not to disturb me, you would leave my bed
While I lay there rigidly, feigning sleep.
Words that allow us to find a confession of sadness and loneliness are found in the phases, the images, below:
Moonlight keeps me awake...A child weeping at nightmares...Everything tinged by terror or nostalgia...impersonal desolation...chills the spirit..., and ...feigning sleep.
The moonlight that has kept her awake, is now more chilling to the speaker than the light of day: perhaps she sees in the moonlight as a constant reminder of his departure and her loneliness. The reality of daylight is not as "cold / As a full cup of moonlight."
Addressing him with "you," the speaker is telling this departed lover how she is feeling; if she had to "coax" him to hold her, and if he was "[a]lways withholding something," her words will seem a confession of sorts in that he never really let her into his heart, and so we can expect that her confession would not be a welcome bit of news for the man who has left her, seemingly never connected to our speaker in any way other than that of a physical nature.