Alisha S. writes about the pain of always trying hard and still feeling like it isn't enough. The speaker lives "in the shadows," watching other people do better, and describes the feeling in harsh words: hate, anger, disgust, rage, hurt. Failing to measure up is pictured as a stake through the soul and a "perfect poison" for both heart and sanity.
The most striking part comes near the end. People smile and say "that was amazing," but the speaker hears a hidden "but" that they never actually say out loud. The praise feels fake, even mocking, because the speaker is sure it comes with a condition: it will never be good enough. That idea is reinforced by the title, «But.», which turns one small word into the heart of the poem.
The mood is bitter, defensive and exhausted. Short, blunt lines and the angry "How dare they!" make it feel raw, like someone finally saying what they usually keep inside.