Answer:
"The Lightning Thief" written by Rick Riordan is a fantasy-adventure and a first young adult novel published in July 2005.
Step-by-step explanation:
In Chapter 13, Percy encounters the Mother of monsters, Echidna, and her son Chimera. Chimera blasts a hole in the side of the arch and Percy's sword is dropped in the hole. This fight with Echidna and Chimera is a low point in the life of Percy because he feels that he is not good enough to be a hero. Percy doubts himself as he can not fight with Echidna and Chimera. Echidna provokes Percy to jump in the hole if he truly is from the lineage of Poseidon. This shows that though Percy is chosen one when faced with failure he doubts his calling. He is discouraged easily.
I think his doubt is reasonable, as he is the chosen one and if he makes clumsy mistakes then his people will not trust him. But he proved his doubt to be wrong later in the story.