In the book "The Lost Hero" by Rick Riordan, Leo expresses his fatigue and mental strain during a challenging time. He speaks to himself out loud, indicating his frustration and the effects of a long and tiring night. His remarks suggest that he is feeling overwhelmed, potentially to the point of experiencing hallucinations.

Piper, noticing Leo's unusual behavior, responds with curiosity but receives an evasive answer. Leo downplays his state by saying “it’s cool,” reflecting a casual attitude despite the seriousness of his situation. This interaction highlights the themes of camaraderie and the pressures the characters face in their journey.