Where might the speaker have been going and what work did he have? Who was he going to see? Did anything happen to him?
The speaker is probably Frost himself. He was a poet and a teacher. Most likely this poem records a real experience, which seems very similar to the one described by William Wordsworth in his sonnet beginning, "The world is too much with us." Frost lived in rural, rustic, thinly populated New Hampshire for many years. He wanted to lead a simple life and devote as much time as possible to his creative writing. The landscape he describes is one of open countryside with isolated farmhouses scattered here and there. It would be necessary for Frost to go into town to buy all the things that are needed in a home, especially food. The line "The darkest evening of the year" indicates that the time is just a few days before Christmas, as does the fact that this is a very light early snowfall. So the speaker could have also bought some presents for his family while he was in town. There was probably only one town serving the inhabitants for many miles around, and presumably the speaker has been there to do his shopping and is now on his way back home in a sleigh drawn by a single horse. Automobiles were becoming common in the days when this poem was written, around 1927, but Frost seems like the kind of man who would prefer old-fashioned things, including living on a little farm, chopping his own wood, as he wrote about in one of his other poems, and repairing his own stone wall, as he wrote about in another. The appeal of Frost's poetry rests largely on the way it reminds us of the beauty and the rationality of leading a simple life close to nature--something most of us have lost, or never had, or never can hope to have. Wordsworth chose that simple life. So did Thoreau. William Butler Yeats fantasized about leading such a life in his beautiful poem "The Lake Isle of Innisfree." We enjoy the illusion of stopping with Frost to take time out from the hurly-burly of modern civilization and feel renewed by having experienced the beauty and silence and simplicity he evokes.
A lot of readers say that the narrator is probably a country doctor making house visits, but as it goes with poetry, this is just speculation. (The interpretation is open to each reader to read into it whatever he or she can relate to.) At any rate, this idea corresponds well with the narrator's wishes to linger in the woods being overcome by a sense of obligation to "get on with it." Perhaps he/she has patients waiting who depend on prompt attention. A good doctor has to put personal wants and needs aside. In conclusion, the narrator says:
The woods are lovely, dark and deep
But I have promises to keep
And miles to go before I sleep
And miles to go before I sleep.
The repetition of the last line reiterates the aspect of weariness and waiting before rest. Some psychoanalysts consider this even as a kind of death wish - a desire to escape from the problems and obligations of life itself.