Blame.
Addicts obviously play the blame game, but I think we also have a tendency to place blame. Specifically, we blame them for all of our suffering when in actuality, after we've learned the truth, we are making a choice to allow this repetitive and predictable outcome. Once we know the truth, we have nobody to blame but ourselves.
ETA: Until I came here and started down this path, I blamed my sister for destroying our entire family. Overreact much? It was hard to hear at first, but now it seems so obvious to me. How could I have been so blind to the fact that she didn't destroy my family any more than I caused her addiction? I was giving her a lot of power and pain, neither of which she needs or deserves.