i think he's saying he's turned callous and hollow in a sense. he 'used to have a heart', meaning he used to care about her and treat her properly and he's suddenly realized how much he's changed and how much he hurts her now and he doesn't want to continue that so he's telling her to 'revive' him, so they can go back to before and he can treat her the way he should again.
i think he's saying he's turned callous and hollow in a sense. he 'used to have a heart', meaning he used to care about her and treat her properly and he's suddenly realized how much he's changed and how much he hurts her now and he doesn't want to continue that so he's telling her to 'revive' him, so they can go back to before and he can treat her the way he should again.