Cornsnake Striking (prey) Problem?

My cornsnake is the sweetest snake alive. When it comes to prey however, he's very aggressive. I switched him to frozen mice, which he does well on (he's 2 years old btw) but every now and again he won't eat and I'll get some live mice to entice him. Lately he won't eat frozen and seems to have a problem when striking the live mice I put in there. He follows the mice around like he is in fact interested, but when it comes to striking it, he's not very "enthusiastic" about it.