The title tells us where we are: a sled ride through a place called Plummer's Hollow. The poem itself skips the ride and begins afterward, once the speaker is back indoors. What it holds onto is a small, odd detail: the breath that froze in his beard during the cold is now melting and dripping, long after he has returned.
The speaker never says how he feels, but the choice of detail suggests a quiet contentment. He seems to be still carrying the outing with him, as if the cold doesn't want to let go. The dripping is a slow, physical reminder of the trip, and it hints at warmth arriving after hardship.
The mood is calm, intimate and a little humorous. It's a short, still moment, the kind of thing you notice only when the excitement has passed. The short lines let the drips fall one by one, and the poem ends on that image without explaining it.