Disappointment is good. Means we have hope, means we still alive. Just like we hope Pixar and Disney will always making good movies, and it turns out they can't always do magic. We hope to see a brand new Superman with element of realism, but many of us felt disappointed. We expect the gasoline price stays low, but it rose anyway. Also we wish many people to see our art work(s), but apparently we (I) still need to work it out.
But somehow we never stop hoping and believing. Even though we have been disappointed so many times.