The speaker confesses to a habit that sounds like an appetite: "I dine on gall." Gall means both bitterness and nerve, and here it suggests a steady diet of outrage. The speaker checks "in what war / they are," as if scanning the news or the crowd for the next fight, and takes a kind of nourishment from whatever angry thing turns up.
The twist is in "fat / am I now in my fear." The speaker is well fed, but what they've been eating is fear, not satisfaction. The outrage doesn't protect them; it swells their anxiety. Then comes the blunt last line, "Anger is life," which could be a defense or a grim admission. It's hard to tell whether the speaker believes it or is just stuck in it.
The mood is tense and self-aware, almost darkly funny. The short lines feel like quick bites, and the poem leaves you wondering what the speaker would be without the anger.