A person who faces difficulty and loses hope or confidence has become discouraged. He may believe a desired task cannot be done or may find that outside forces prevent him from reaching his goal. Similar to a person who is disappointed, a discouraged person is unhappy about the situation. However, the discouraged person may lose the will to try even before he makes an attempt.
When a person expects a certain result, and does not receive it, she becomes dissatisfied. Even if she achieves partial success, a person can be dissatisfied with the results.
When a person's goals are prevented by an outside force he cannot control, he may become frustrated. In some cases, a person can be frustrated because of an inescapable event or the actions of another person or entity, such as government bureaucracy.
Any situation where something disturbs the normal order of things can be called "an upset." This includes a change of plans, an unexpected winner or a body failing to function properly. This reversal of the expected usually occurs suddenly and causes the people involved grief, displeasure and unhappiness. Similar to someone who is let down, a person is upset when an unforeseen event changes the outcome and prevents what she wanted.