I think expectations, though important, can be one of the worst things to have. We often expect not only far more than what people can give, but usually something entirely different than what they were destined to be.
We see in them something they will never seek to be, something they will never reach out to become....we set the bar high, yes, but in the wrong place for them.
We often expect from others what we feel we would do if we lived their life or went through what they had been through, and we deduce from their experiences what should be their next goals. Thus, we are expecting a result from them that perhaps they were never meant to give.
So, we become disappointed when they don't live up to our expectations.
If I am friends with a tree and I expect that this tree will grow forever beside me, I would become disappointed when it is cut down to become a Hope Chest for a young woman longing for a husband. I had not foreseen such a thing, my expectation of the tree's life was different than its destiny, so I become hurt.
We can want the best for others, but it isn't up to us to decide where they go.