There are many possible themes to be read in the poem "Stopping by Woods on a Snowy Evening." One of the most common interpretations is Personal Responsibility; the narrator is enthralled by the snowy woods, and stops in his civilized pursuits to take in the beauty of a natural landscape, but he can't stay. This can be read in the final stanza, which contrasts the beauty of the woods with the narrator's obligations:
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.
(Frost, "Stopping by Woods on a Snowy Evening," eNotes eText)
Although the narrator appreciates and loves the woods for their natural beauty, he needs to continue his journey, because he has "miles to go before [he] sleeps." He must continue working as a part of society because that is the role expected of him; his obligations leave him only moments to enjoy the simpler things in life. Perhaps in time, if he works hard within societal constraints, he will own a plot of land in the woods to sit in, enjoying nature for its innate perfection; for now, though, he must continue to travel to keep his promises.