The danger of setting your own expectations is something that affected me in one of my first shoots.
I had in my mind the kind of shots I was hoping to make, and wouldn't let it go.. Well, I never saw anything like the shot I wanted to make. That’s the danger of setting expectations — you go thinking you’re going to get a particular type of shot, but then the reality of where you wind up sets in you’re disappointed with your shots, (which I was), and it’s not anyone's fault.
It would of been wiser to have gone more open minded to whatever came my way, instead of standing there saying “This isn’t what I was really looking for. It must be somewhere else here.”
Be prepared YES for sure, fulfill the brief, apart from that go with the flow, review where you need to head for contrast between the frames and alternatives to the great shot your loving now, but will you love it next week, next month. Give yourself or the client alternatives.