"You have no faith," Echidna told me. "You do not trust the gods. I cannot blame you, little coward. Better you die now. The gods are faithless. The poison is in your heart." (13.139)
You bring up a good point, Echidna. One of the biggest things that Percy has to learn over the course of his quest is faith: faith in himself and faith in the gods. And, boy, does he do a good job of learning this. How does faith work? Can you just say you are going to believe in the gods and then believe in them? How does Percy gain faith in himself and in the gods?