In just four lines, Dave Bonta sets a small insect beside a human act of letting go. The first two lines say a moth cannot think ahead or choose the life she will lead. She simply is what she is, moving by instinct, without plans or options to weigh. There is something tender in that, and a little sad, since the moth has no say in her own course.
The second half turns to the speaker's own words, which are "let go at last." That phrase suggests relief, maybe after a long period of holding back or revising. Yet the words are "not lost to the night," so they don't vanish. Like a moth drifting into darkness, they travel beyond the speaker's control but still exist out there.
The mood is quiet, hushed and gently hopeful. The speaker seems to accept that once words are released, they, like the moth, will live their own life.