Sleep never quite arrives in this poem. The speaker lies in bed, eyelids drifting shut and then opening again, and in that restless gap starts asking why they exist at all. It's the kind of big, lonely question that tends to show up when everything else is quiet.
The night around them feels almost alive. Stars "blink," the moon "stares," and the night itself is "listening" for the speaker's breathing. That can feel watched and a little uneasy, or it can feel like company, and the poem leaves both readings open. Then a memory rises up and brings tears, which suggests the sadness was waiting just under the surface.
The last couplet sums up the problem: the mind is awake while the body sleeps, so the two are out of step. The short, simple lines and repeated "-ing" endings make the mood slow, hushed, and tired, like thoughts circling in the dark.