My daughter's therapist explained it like this to me: "Have no expectations" really means "have realistic expectations" -- and "realistic expectations" when you're dealing with an abusive alcoholic means: They will f**k with you as long as they are alive. Every time you think it's over and you can relax, they WILL reappear and try to screw you over somehow.
If you expect that, then you don't get so surprised and anxious when it happens -- you can go "oh here we go again, the old a-hole dance" -- rather than (like I do) not sleep for weeks and barely function during the days.
That was her take on it.