What mixed emotions does Percy feel when he talks to his dad?

In chapter 21, Percy finally meets his father, Poseidon. At Mount Olympus (above Manhattan, of course), Zeus and Poseidon are seated on thrones.
When Percy enters, both gods appear to have been arguing. Percy kneels before Poseidon and is rewarded with a rebuke from Zeus. However, Poseidon maintains that it is only right that Percy acknowledge his own father first.
Upon meeting his father, Percy experiences mixed emotions. He feels great reverence, but he also feels a little intimidated by Poseidon. Above all, Percy feels detached from his father, as Poseidon has been alienated from his son for much of the latter's young life. It is also evident that Percy also feels a desperate need for his father's approval.
As the two finish discussing Kronos, who has proclaimed his own return from the pit, Percy feels a twinge of sadness. Poseidon admits that he is sorry for bequeathing Percy a hero's fate, which is "never anything but tragic." Percy's sadness does not last for long, of course. Poseidon's last words bring a measure of joy to Percy, however.

"You did well, Perseus. Do not misunderstand me. Whatever else you do, know that you are mine. You are a true son of the Sea God."

So, Percy has mixed feelings when he talks to his father: awe, sadness, pride, respect, and finally, a measure of joy.