My advice is keep holding him.... IF he struggles, don't let him go. If you do let him go when he struggles and try to bite you, you will teach him that biting and struggling means I get to go free. Keep the session short at first and gradually start by holding him longer and longer outside the cage. I know someone who tamed an aggressive iguana in several days. Now, he's eating and growing and shedding like crazy. They can pick up on your fear, so act like your not afraid...like King Richard I. They are kindda like dogs, which can pick up on your energy...fear or whatever.