I recommend you to research the term "intentional living".
The point is: living a meaningful life is (to a certain degree) about being in charge yourself. You don't do things because you can, or because they happen to you.
You lay out a (rough) plan what you want for yourself. And then you apply an "agile" mindset: you observe how things turn out in the real world, and then you make the necessary adjustments.
In the German language the term disappointment translates to Enttäuschung. Meaning: a disappointment is the ending of a deception.
In other words: one element of disappointment is about starting with unrealistic expectations. You basically lie to yourself about all the great things that should follow out of something you do.
Long story short: step back, and consider what you can get back realistically from engaging here. And then ask yourself how much that is worth to you. Then act accordingly.
Finally: I am not saying that should never trust others, or not have expectations. But you better be aware what exactly you expect, because only then you can do that self assessment to determine who realistic your expectations are.