Percy Jacksons personality is questionable. Sometimes he is calm and normal. Some times he really angry.
In the book Percy's personality is sometimes calm and normal like when Annabelle was feeding him the popcorn pudding and when he was playing pinochle with Chiron.
He is commonly angry like when he goes home and gabe makes him do stuff for his poker buddies and when Clarisse makes fun of him he gets really angry.
That's why Percy's personality is questionable. Percy's conflict was different then ordinary humans because he had ADHD. Most of the half bloods have ADHD and dyslexia.