Disappointment comes from expectations not being met.
Despite how you act as a person, others can only meet you at the level they are meeting themselves.
Often we are impatient with others who don’t see things how we see them or may not be so self-aware or haven’t experienced what we have. We all see the world a little differently.
However, they will have experiences that we haven’t. Be aware of and see things we may not be able to.
Before you feel disappointment again from others, perhaps reassess your expectations, allowing for that how we see things is not the only way.