The speaker looks back on a time when ordinary things felt dangerous. The outside world seemed too bright, too unpredictable, and too much. Sunlight might burn them, other people might tear them apart, and even a gentle touch might poison them from the inside. The images are extreme on purpose: they show how fear can make the safest things feel like threats.
The middle of the poem turns inward. The speaker describes living in a "prison the shape of my body," crying, breaking things, and sleeping among the shards. Then comes the broken repetition of "i used to / i used to," as if the speaker is stuck or struggling to say more.
The ending is defiant but quiet. The speaker invites the insults, "neurotic, a failure, pathetic," because none of them cancel out one simple fact: "today, i saw the sun." The mood moves from dread and pain to a small, hard-won triumph. Stepping outside is the victory.