The speaker says something quiet and honest: nobody really knows how exhausting it is to keep up a front. They act okay and play the strong one, while inside they feel they are barely holding on. The poem is only a few lines long, and that brevity suits the feeling. There's no big drama, just a tired confession.
The line breaks do a lot of the work. The sentence slows down and falls apart as it goes, with "you're close to" hanging alone before "the edge" arrives at the end. It's almost as if the speaker hesitates before admitting how close they are. The shift from "I" to "you" is also interesting, since it might be a way of speaking about their own feelings at a slight distance, or of reaching out to anyone who feels the same.
The mood is weary, lonely and fragile. It isn't loud or angry, just worn down by pretending.