What does it mean to dream about disappointment?
Disappointment in a dream usually carries a gap between what you hoped for and what came, and what fell short is often the thread worth following.
Four ways to read it
Each reading below comes from a named tradition and a cited source, so you can see where it came from and decide what fits your dream.
Freud
Freud would read disappointment as a wish met by its own limit, the desire shown but not satisfied. He held that the mind can stage a longing only to confront the bar against it. The let-down may mark a hope the waking self has not let itself name.
After Freud, The Interpretation of Dreams (Brill trans., 1913), public domain.Jung
Jung would see disappointment as the meeting of an inner image with reality's edge, where an expectation has to be revised. He treated such moments as part of growing, the loss of an illusion making room for something truer. The feeling can mark where a hope is asking to be reshaped.
Jungian concept (our summary).Modern
Continuity research ties dream disappointment to waking setbacks and hopes that went unmet, which the sleeping mind keeps turning over. Some emotion accounts suggest dreaming helps the let-down settle over time. The feeling is best read against what has lately not gone as you wished.
Continuity hypothesis (our summary).Mythological
Myth was full of dashed hopes, the prize that slipped away, the promise broken by a god. Tantalus reaching for fruit that drew back caught the shape of it exactly. Across cultures such tales taught that longing and loss often travel together.
Rosmerta Publishing editorial synthesis (after Bulfinch; Brewer).