Dave Bonta's short poem imagines a stone that grows a mouth, and the odd thing is what it grows it for: mist, specifically, "not for the haze." That small distinction matters. Mist is close, wet, something you can feel on your skin. Haze is vaguer, more distant. The stone seems to open itself only to what actually touches it.
The second stanza turns the mist into a "mistress," a playful pun, and says she is enough, even "on that irregular ground." The landscape is uneven and rough, yet the relationship holds. Then the speaker steps back and admits something with a shrug: being loved is "a strange blockhead luck." A blockhead is dull and stubborn, much like a stone, so the speaker may be quietly comparing himself to the stone. Love lands on us without our earning it.
The mood is tender, wry, and a little amazed. The speaker sounds humble, surprised to be cared for, and happy about it without making a fuss.