Heartbreak also happens when we trust people and they break it. Over and over again.
It is not about their actions anymore. It isn’t about what they said and did.
Now it has become about you not being able to trust them anymore, after all the time you trusted them, gave them first chance, second chance, and so on.
Heartbreak is about trust being broken. Once broken, unless the other person makes significant effort to repair it (more often than not they don’t), it is heartbreaking.