I loved this poem immediately when we learned it as children in school. And my parents recited it to us when we were young. It's a beautiful poem with lovely images that captures a moment in the life of the observer, who knows he is too busy living his life to 'explore' the woods. He ends by saying he has 'miles to go before I sleep', which is a metaphor for his eventual death. So I interpret the poem to mean that he can stop and reflect on his life at different points in his life, and that perhaps nature serves as a means for him to do this, but that he wishes to keep going, to keep living, to honor his promises, before he rests forever.
Stopping by Woods on a Snowy Evening
Whose woods these are I think I know.
His house is in the village though;
He will not see me stopping here
To watch his woods fill up with snow.
My little horse must think it queer
To stop without a farmhouse near
Between the woods and frozen lake
The darkest evening of the year.
He gives his harness bells a shake
To ask if there is some mistake.
The only other sound’s the sweep
Of easy wind and downy flake.
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.