It does seem to be working. You seem to have opened a gate to self development. When the student is ready, as they say
While unpleasant, anger and sadness powerful and important emotions. Sadness is an indicator that you have been wronged. And anger is what allows us to set boundaries when a line has been crossed. I know it probably feels like the anger is out of your control right now... but honor that you are feeling it. It needed to be acknowledged by you. When it is acknowledged, it can let go. It no longer needs to fight for your attention.
I would also write down anything you can connect to this anger and sadness. Who are you angry at, and what are they doing that is triggering it?
Write it all down, whatever comes to mind, as many as come to mind. Then you can release each one with next rounds of breathwork, shadow work, or whatever process you like.
To answer your question more directly, I do feel that triggers in the external world are usually what make me aware of the internal. It doesn't have to work that way, though. But as the external is a reflection of the internal, it's just as good that way.
The best part is, once you release the anger... those things that are triggering you start going away too. So there is a light at the end of the tunnel :)