The Party Across the Street Meaning & Interpretation

"Last night, I dreamed there was a party in the building across the street. The music was loud, and colorful lights flashed in the windows. I was standing on my balcony, watching people laugh and dance. Then I saw my ex on the balcony of that building. Our eyes met across the street. My ex smiled and waved at me, like nothing bad had ever happened between us. In the dream, I decided to go to the party. But every time I opened my door, I was back on my balcony again. I tried three times. Walk to the door. Open it. Balcony again. It made no sense. My ex kept waving, calling my name. But the street between us became longer and longer. First it was ten meters. Then it looked like a river. Then the buildings moved apart like boats on the water. Suddenly, my phone rang. It was my ex. "Why won't you come?" the voice asked. "Just cross the street!" I looked down. There was no street anymore. Only deep, dark water below. A paper airplane flew from my ex's balcony and landed near my feet. I opened it. Inside it said, "We are both at the same party. You just don't know it yet." I woke up before I could understand the message. My alarm clock was ringing, but it sounded like party music for a few seconds. All day, I kept thinking about that strange sentence. What party were we both at? I still don't know."