Promises are not the only things that one keeps. Secrets, both implicit and explicit, are another. And there is something secretive, some uncertain thread in the tone of the poem: the narrator thinks he knows to whom the woods belong (line 1); he has stopped somewhat clandestinely just beyond the border of the other man's woods, even to the surprise of his (the narrator's) horse, who is quite probably used to going right onward, home for feed and warmth (lines 3, 5, 9–10); this is, it turns out, "the darkest evening of the year" (line 8), which comes with its own mystery.

It is almost as though the narrator had something on his mind when he paused by the woods, something about which he is deep in thought that he does not clearly delineate to the reader (except for the final stanza about keeping promises and miles yet to go) but that weighs enough on him to draw him to a dazed halt at the edge of these woods. Even the final lines, repeated—"And miles to go before I sleep" (lines 15–16)—are full of secret possibility: Are the miles to which he refers literal geographical miles, in terms of an actual distance? Or perhaps milestones in some venture or relationship that he needs to meet? Or psychological miles, maybe, and much more to think about before he makes a decision?