What even is it?
Is it something other people do to us, or something we create through expectation?
I'm my experience, it's always such a mix of both. People talk about how everyone is so jaded etc., but trusting and trusting and trusting other people to be and do what they say can be exhausting.
Every time it happens, I force myself back into my own heart. That's where my joy stays. That's where my happiness flows from.
I hope if you are feeling heartbroken, you allow all of those feelings to bring you back home to yourself.
We are all we have.