Final answer:
Poseidon is forbidden to help Percy directly, meaning he can't intervene overtly or provide protection; Percy must rely on himself, similarly to mythical heroes like Perseus.
Step-by-step explanation:
When Percy learns that Poseidon is forbidden to help him directly, it means that Poseidon cannot provide direct assistance or protection to Percy. This suggests that while Poseidon may still influence events or offer guidance indirectly, he cannot intervene in an overt or powerful way that would clearly come from his hand. The gods, much like in the myth of Andromeda and Perseus, have rules that they must abide by, which often include restrictions on directly meddling in human affairs. This theme is prevalent in mythology, indicating that the heroes must often rely on their own wits, courage, and sometimes the indirect help of the gods, like Perseus received from Athena and Hermes.