Since Percy had arrived at Camp Half-Blood you didn't understand why he didn't like you, you were nice to him and he would walk away or tell you not to bother him.

Today some were training their skills with different weapons, Percy looked at you, how your hair shone with the sunlight, your movements, he liked that... No! He couldn't think those things about you, he didn't like you.

Due to being distracted, he tripped and fell to the ground, you saw it.