The speaker is mourning someone who has left, and the poem is about how much that person changed the way the world feels. Reality, for the speaker, is "a really dark place." When the loved one was around, it stopped being so heavy, because life and dreams seemed to overlap. Now that "your gone," that blend has broken, and the speaker is stuck with only the harsh half.
The central image is flight. The other person is described as "my wings," which suggests they gave the speaker lift, freedom and the chance to escape everyday worries. Without them, the speaker feels "anchored down," a heavy, sinking picture that contrasts with the clouds they long for.
The mood is wistful and quietly desperate. The language is simple and repetitive, and the short lines make the loneliness feel plain and unguarded. The final line, "And I can't fly," lands like a sigh, ending on helplessness rather than hope.