The speaker looks back on a childhood friendship, listing small, happy moments: selling lemonade, swimming in the pool, walking to school, playing Pokémon on a DS. The repeated "Us" at the start of the lines makes these memories feel close and shared, and the simple, run-on style sounds like someone remembering one thing after another. The speaker says they didn't think much back then and "just have fun," which makes the time seem carefree.
The last line changes everything. Now the friend sits on the climbing frame with other friends, while the speaker sits alone, trying not to cry and feeling like "a loser." The "Us" disappears and the two people are separated. The title adds to this feeling. Throwing away supermarket flowers suggests grief or hurt, though the poem never says exactly what happened. The mood begins warm and nostalgic, then turns sad and painfully honest, as the speaker sees how much has been lost.