The speaker describes an imagined world where everything goes the way they long for. Someone holds them, kisses them for the first time, and runs with them into the woods, sharing secrets along the way. It reads like a fairytale, and the repeated "you" makes the fantasy feel tender and close.
Then the mood shifts. The utopia fades first to grey, then to black, as if the dream is running out of light. The final secret is the blunt line "I don't love you," and it lands harder because everything before it was so gentle. The poem suggests the speaker may be imagining this love because it isn't real, which makes the ending a double loss: the fantasy collapses, and so does the hope behind it. The last two lines tie the broken dream directly to a broken heart. The overall feeling is wistful, then quietly painful.