I think for me, as a sister of an addict/alcoholic brother, I wanted to fix him and make it better. I knew very well that any kind of control would not work, but yet I tried. There was no such thing in my vocab to quit on someone in your family.
Now as a fiance of an addict for 8 years...it was also wanting to fix him, care for him, to show him if I am all he wants me to be then it would be enough for him to quit using, it was an addiction that I had for him. I knew here too that control would never work, nor the threats of leaving ect....
Then I started working my program after crying out for help. And here I am today, in such a better place. =)
Good question Roo!! I hope you find that answer you are looking for deep inside of you..