Disappointment is a response when one has lost hope.
Emotions which branch out from hope are disappointment, envy, confidence, and helplessness.
Disappointment is an emotion which branches out from hope when it disappears. People feel disappointment when the result of something is different from their hope, such as failing a school's entrance examination. When disappointed people droop their shoulders, and reduce the pace of their actions. This has the effect of allowing the person to correct the appraisal and reflect on his or her behavior patterns.
Prediction is indispensable to disappointment. People don't feel disappointed when they lose money unless prediction is involved. If people predict unfavorable results the degree of disappointment is lightened, because hope is a profitable prediction for the self. If people have absolutely no hope, they don't feel disappointment.