What is a theme of "Stopping by Woods on a Snowy Evening"?

One theme is the theme of isolation.  

This is probably my personal favorite theme of the poem. It's a lonely poem. The speaker is a man who has stopped with his horse beside a lonely wood. He doesn't know who the woods belongs to, but he is sure that the owner lives in the town that is in the area.

Whose woods these are I think I know.   

His house is in the village...

One theme is the theme of isolation.  

This is probably my personal favorite theme of the poem. It's a lonely poem. The speaker is a man who has stopped with his horse beside a lonely wood. He doesn't know who the woods belongs to, but he is sure that the owner lives in the town that is in the area.

Whose woods these are I think I know.   

His house is in the village though;  

There's nobody else around. In fact, he is so alone that the only sound that he hears is the wind and the harness bells. 

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.  

I never get the feeling that the man is scared by his isolation. In fact, I get the opposite feeling. I think that he enjoys his isolation and alone time. I feel that is especially evident by the positive way in which he talks about the dark and snowy woods.

The woods are lovely, dark and deep, 

The ending of the poem seems to indicate that he is tired and not looking forward to keeping those promises. Those promises are likely reminders of his busy, people-centered life. I always get the feeling that the man is thinking those final two lines with a heavy sigh.