A speaker describes years of commuting on the London Underground, or at least a train, and the habit of catching sight of their own face in the window opposite. For forty years that reflection has shown them growing older, and eventually they stop looking. They simply don't care to see it.
Then the poem turns. The speaker looks up again, because now there is someone else in the glass, a second face beside their own. The reflection is no longer something to avoid. It becomes proof of something good: "I did alright. I deserve you."
The mood begins flat and tired, almost resigned, then softens into quiet relief and tenderness. The short lines and plain wording make the final admission feel honest, even a little shy. The speaker doesn't say who "you" is, so a partner, a child, or someone else could fit. What matters is the change: the window that once showed time passing now shows a reason to feel proud.