Sometimes it is hard not to get disappointed in things that are going on.
Everyone thinks everyone else's life is perfect. But it is not everyone has their own problems going on in their lives. It can be very disappointing when things don't go the way you want them to go.
A lot of times it is more how you think of yourself and not how other people look at you. We sometimes set our views higher than what we should and then you become disappointed in ourselves.
I know sometimes people do get disappointed in other people and that is when you don't live up to what they expect of you. Or a person promises something and they don't do what they promised to do.