The meaning of "Stopping by Woods on a Snowy Evening" is generally personal, depending on the reader's perception. Attempts to read more into the poem than is visible on the surface, or more than can be easily interpreted from the available themes, often become exercises in justification without other merit. However, there is a commonly accepted "deeper" meaning other than the appreciation of nature and the resignation of personal responsibilities.
It can't strictly be called a "hidden" meaning, but the poem as a metaphor for life and death is not in the text itself and so must be inferred. The narrator is tired of working; he seems to be longing to go into the woods and forget all about his obligations. His obligations are his life; he has "promises to keep" because his life is continuing. His "sleep," which he desires to experience in the dark, snowy woods, is the daily cessation of his "promises," or his life. When his life of promises is finished, he can have the eternal sleep of death.
Interestingly, the poem is often used in eulogies for the recently deceased, and the imagery is thus sometimes interpreted as depressive instead of enthusiastic. Justin Trudeau, son of Canadian Prime Minister Pierre Trudeau, paraphrased the poem at his father's funeral: "The woods are lovely, dark and deep. He has kept his promises and earned his sleep."
Well, since this is a JOURNEY, we should look for a more figurative (not really hidden) meaning. Consider that the speaker is pausing - some might say procrastinating - on his or her way to complete what seems to be a utilitarian task. Do we want to think of this as a pondering along en route to one's destiny? The repetition of the last two lines has been dissected since the poem was first published; it does suggest that second "miles to go" refers to life's unfinished business. Look at the earlier part of the poem - what other clues do you see that might indicate that Frost is talking about more than just a leisurely sleigh ride through the woods?