The poem sets two people side by side and shows how far apart they really are. The "you" sleeps, dreams, hopes and smiles. The speaker lies awake, loses their dreams, loses hope, and smiles only on the surface. Nearly every pair of lines works the same way: something ordinary and good for one person turns into its painful opposite for the other.
The speaker feels exhausted, empty and hidden. The line about "i'm fine" suggests the "you" is fooled by a mask, while the speaker is close to giving up entirely. The speaker seems to be talking about suicide, though the poem only hints at it through "my last breath" rather than saying more.
The ending shifts from despair to a kind of plea. The speaker imagines the "you" crying and eventually realizing how much they mattered. The mood is heavy, quiet and lonely, with a sense of wanting to be noticed before it's too late.