The speaker is looking back on a relationship that has fallen apart, and they take the blame for it. They say they can't forget what happened, and every time they see the other person, the memory comes back. One fight in Barcelona stands out, though the poem never explains what happened there. What matters is how heavily it still weighs on the speaker.
The feeling is mostly guilt, mixed with longing. The speaker admits their insecurity and wishes the other person could understand it. The central image is a simple pair of colors: "You painted us gold / And I made us blue." One person made the relationship bright and valuable, the other turned it sad. The repeated "I wish" gives the poem a quiet, helpless tone, like someone who knows they can't change the past. The ending is soft and sorrowful. The speaker doesn't argue or defend themselves, only apologizes and wishes things had worked out.