Is it considered unhealthy anger, for instance, if someone is upset about a small incident involving someone who is no longer in his life and is only upset when he thinks back on the incident at random?

This does not seem to me to be unhealthy anger, which usually is defined as persistent and deep anger.  From your description, you are not continually or deeply affected by what happened.  To have occasional anger, for a short time, when reflecting back on an injustice is common.

Please follow and like us: