Disappointment is about anticipated rewards.
Sometimes the anticipated rewards are the result of our ambitions, aspirations, dreams, desires, experiences. We are active part in building up our expectations, to the point that it often becomes impossible for the actual thing to satisfy them.
Sometimes they are set by others with their ads, content, hype-building tactics, public relations, supposed culture. They prepare a mental image for us that buys us in and eventually turns out to be just too good to be true.
Disappointment is a fundamental part of life. The first type helps us stay grounded, adjust our course, understand how things work. The second type tells us about relationships, who to trust, to what extent and in which circumstances.
And most of all, disappointment is a reminder that while we often govern the inputs, we have little to no power over the outcomes.
That is fine.