In love with an addict

I fell in love with a herion addict... he wants to stop but he can't. He is so sweet whether he is on it or not. Always makes me laugh and makes me happy. I care for him so much but idk what to do. I'm scared he will die. How can I be in love with a herion addict. How do I fix him? He says he controls it which there really is no control when you Have to have it almost daily. What do I do?