The expression that helped me through times like you are experiencing was "Say what I mean; mean what I say, but don't say it mean." If I stopped focusing on my daughter and what she was doing and focused on me and what I said I was going to do, it helped me to not get sucked into the drama. I had to be true to what I established was best for me. So "no I am sorry; I am not going to do that" then walking away, became my response. Once my daughter knew that I meant it and it was no longer my usual idle threats or ranting and anger,(followed of course by giving in, because I felt guilt and shame for my behavior) she stopped relying on me to enable her addiction.