The speaker describes a strange, repeating task: making a cellar into a private place, then digging it out again, from one side to the other. The work never seems to finish, and while it goes on, life above ground slips by. "Go upstairs to grow old" makes ordinary living sound like a quiet sentence, something you do after the real work is over.
The last lines turn toward feeling. The speaker wishes for night "instead of all the good things / which own our home." That word "own" is striking. The comforts of a household feel less like gifts than like owners, and the speaker is the one possessed. The cellar, dark and hidden, becomes a refuge from that pressure.
The mood is hushed, weary and a little secretive. The poem doesn't explain why the speaker wants to withdraw, which leaves a sense of longing for darkness, privacy and release from what looks like a perfectly good life.