Expectations

Why do we expect things from other people?  Especially things we don't think we will really get? I expect my spouse to stop drinking. I don't think she will stop.  Every time she dries up for a week or two I begin to feel hopeful then I come home from work and she's obnoxiously argumentative, cocky and a little aggressive....then i start to look for the alcohol.  So why is it we want to think good about people even when we know it won't happen? Why do we hold out for their change?
I think we, as humans, tend to want to idealize everything we are involved in. When I buy a new car I try to find every reason why it's the best car out there.  The same with my family. When I have committed my being to them I tend to idealize what they are and who they are to try to ensure my satisfaction with them, since I can't trade them in for something else (hence: commitment).  But in doing so, I tend to fabricate beyond that which is reality so when reality become evident, it's annoying or even hurtful to me.  For that reason I think, we as people, need to stop idealizing our family and become more accepting of them and who they are, warts and all.  Once we accept them for who they are, we will learn that it doesn't matter what they do, we will still love them, even when it hurts a little or we are disappointed.