It is not wrong to expect, problem arises when one expects that expectation to be fulfilled. There is a very thin and subtle line separating the two. The first expectation breeds motivation and desire to achieve, grow and prosper. The second usually results in all generally considered negative emotions.
It is natural to expect. But when this expectation is not fulfilled, then the problem arises. Not because we expected something, but because we expected our expectation to be fulfilled.
They are two different things, but it is rarely that we see through the line separating them. Once this bifurcation is made, we are no longer dependent on anything that we can't control. Fulfillment of the expectation is more often than not beyond our control, so there is no point in desiring it.
For better understanding, a favor done by a person for another person raises an expectation of a 'Thank You' . The expectation is fair, but the person should be indifferent if the opposite happens. The state of the mind should be independent of the fulfillment of the expectation.
This applies to the 'physical world', the 'spiritual world' goes deeper!