You! Lost in a cyclops hope on an island that is yourself.
Ridged in and ridden by tides of terror not your own — but accepted.
On the pronged bit of indecision you earn what you accepted.
Someone is being addressed directly here, and not kindly. The speaker calls out to a "you" who is stranded alone on "an island / that is yourself," held there by a "cyclops hope," a one-eyed, narrow kind of hope that sees only one possibility. The isolation isn't imposed from outside. It's built from within.
The middle stanza deepens this. The "you" is ridden by "tides of terror / not your own," fears that came from somewhere else but were taken in anyway. The key word is "accepted," which appears twice. The poem keeps circling back to the idea that you end up paying for what you agreed to carry, even without noticing you agreed.
The final image of the "pronged bit / of indecision" suggests a bridle or a fork, something that hurts while you hesitate. The mood is stern and uneasy, closer to an accusation than to comfort, though the sharpness hints at frustration rather than contempt.