Almost every line here starts with the word "just," and that repetition is the heart of the poem. The speaker misses someone they used to be close to and hopes, quietly, to see them again. What they ask for sounds small: a chat, a laugh, a bit of time together, things "like old times." But the constant "just" does two jobs at once. It makes the wish seem modest, as if the speaker is trying not to ask for too much, and it also sounds a little desperate, as though they keep circling the same hope because they can't let it go.
The title adds a sad detail. Throwing supermarket flowers from the windowsill suggests something cheap, simple, or unwanted being cast away, perhaps a gesture that didn't work or a hope the speaker is trying to give up on. The poem itself never says why the two people drifted apart. What it creates is a gentle, wistful mood, tinged with loneliness and the ache of wanting a connection back.