I'm in the throes of "National Novel Writing Month" and I have a prince as my protagonist. He's very "hands on" and has a strong "if you want something done, do it yourself" attitude on the battlefield. He insists on being at the head of every charge, he sits in on every discussion of strategy with his generals, and so on. This is mainly because at court no one lets him lift a finger, so he's eager to show he is more than capable on his own and not a spoiled prince who doesn't know what he's talking about. What are some ways this particular character trait can be used against him other than the obvious "if something happens to him, the royal line is in trouble" angle.
His actions are ego driven. Someone with malicious intent within his court could use this psychologically against him.
He may insist on doing things himself/his own way but how much freedom and experience of the outside world does he have? He could easily get lost, led astray, goaded, history is littered with head strong princes who fall under the wing of a power hungry adviser.
This prince, seemed like he is a bit stubborn, and insist doing in his own way. But probably, he is a bit lacking of life experience, and may get lost later on.