Let's talk about disappointment in people. People are quite often disappointed in other people, because they do not
justify their idea of what they should be from the point of view of the disappointed. I am not talking now about cases where certain behavior is an obligation, as, for example, in professional activities. I'm just talking about interpersonal relationships, not associated with any obligations or agreements.
In particular, a striking example of disappointment in people are cases in inter-gender relationships. Again, I have written about this many times, that the motive in intersexual relations is the reproductive instinct, but not something sublime, which is endowed by such relationships with their participants. A person will be disappointed in his partner precisely because he puts some sublime romantic meaning into relations with him, based, as he himself thinks, on his “altruism” meaning.
About what love is for a person
Therefore, he wants to see in the other a correspondence to his idea and his expectations of a certain behavior. Although this reaction to behavior can be completely subjective, not evaluated by any real criteria. BUT is a person who “sacrifices” himself for the sake of his partner so altruistic? In fact, expecting a certain other behavior is no longer altruism, which in principle does not exist in nature. After all, the expectation of a certain behavior is already an attempt to satisfy your need, since you instinctively do not allow other behavior from a person.
Do you want to know - what is love?
And such a person is disappointed not in the person as such, but in the fact that he did not meet his expectations. A person behaves first of all in a way that is convenient and beneficial for him. And the fact that someone believes that his partner should act in accordance with his idea, then these are just his own expectations and ideas about how "should be."