If you don't expect anything from anyone, then they can't dissapoint you.
But then how do you explain the wise words of Goethe? "Treat a man as he is, he will remain so. Treat a man the way he can be and ought to be, and he will become as he can be and should be."
I try not to expect anything from anyone because people will always let you down, but then there are those that surprise you everytime. And of course there are those that will never surprise you.