When dealing with a child you work with anger, frustration, unexplained sadness, etc. don't worry so much about the "why" in the moment. For kids you work with examining that "why" will probably lead to more frustration and questions. Concentrate on the "what" and skills of recovery. These are but not limited to acknowledgement, admittance, reflection on behavior not "why", restitution (if needed), game planning, and practice of some sort. Practice can be as simple as repeating a few steps over and over.
It is certainly not a one stop shop of fixing negative emotions, and for many, there may never be a true fix. Sometimes it is management and preserving longevity. How do you keep your car running longer? Keep up on maintenance. It may never be as good as the day it came off the lot, but it can still look good, and sound good, many years later if you take care of it.
On a side note I think working with your own "why" as it relates to your emotions, can be helpful, but you are also in your own head all day. It is much more convenient.
Here is the full post - http://dougtimm.blogspot.com/2018/02/your-role-in-relationships.html