Eric is a tragic story. A boy, raised in the shadow of the Lord General, is instructed every waking hour on how to be a leader, a fighter. He was likely never allowed to have fun like other boys, and I'm willing to bet his adventures with Kenton were mostly or entirely forbidden. Even then, his father's voice echoed in his mind, preventing him from doing what he wanted.
He spent his entire childhood learning how to be an adult, he never took time to learn how to be a child. During childhood, we form and develop the core of our personalities. Eric was never given the chance. Who he is, though, deep down, is a carefree, happy little boy who doesn't want others to suffer, from his actions or from his leadership.
I doubt his father ever knew who he was. He himself was in league with Sharezan, and likely wanted his son to be a better Lord General than he was.
I once had the thought of what would make Peter Pan want to grow up? Apparently, responsibility. And he was never very happy being grown up.
I apologize, I'm feeling sad right now, and this is what happens when I talk philosophy when I'm sad.