The speaker is addressing someone they once shared a close, private history with, and the poem walks through past, present and future to show how that connection has faded. The past is held only by the speaker, since the other person won't remember those memories. The present is described as wasted, because the two of them ignore each other and don't talk. The future is where the poem turns. The speaker doesn't think there is a "we" anymore, and imagines what comes next as a blank white canvas.
What stands out is the shift in power. At first the speaker seems hurt and left behind, but by the end they claim the role of the artist, the one who decides what goes on the canvas. They choose to leave that part blank and move on to the next picture, one the other person isn't in. The mood is quiet, sad and a little cold, but it ends with a firm, almost defiant sense of taking control. The title, with its discarded flowers, hints at the same decision to let go.