If we knew the complete cause of all phenomena that we encounter, we would never become angry or frustrated with anything or anyone; there would only be understanding. This means that anger and frustration have their roots in ignorance.
When people get mad at someone’s behavior, they often say ‘I don’t understand that he behaves in that way.’ Well, that’s exactly it. They DON’T understand. If they did, they wouldn’t get mad. There would only be understanding.
Suppose you would know the complete history of the universe, having witnessed and thoroughly understood every event that took place in the entire universe from the beginning of time; everything from the smallest collision of subatomic particles to the greatest formation of galaxy clusters.
If then, after 13.8 billion years of exactly understanding that history, you meet a person who behaves ‘badly,’ you would be able to truly understand that person because you would fundamentally know what caused the behavior. You would not get angry at the person, there would just be understanding.
But if you don’t understand what caused the ‘bad’ behavior, then you experience the person out of his or her (historical) context, and so you get angry and frustrated because you overestimate the autonomy the person has in determining his or her behavior.
This, in my view, does NOT mean that if we would truly understand everyone, we would allow everybody to do as they please because we understand them. This is the same principle as understanding a child who behaves badly, but still correcting its behavior.
Now, of course in practical reality you cannot know all the causes of everything that happens all the time. But you can understand that your own ignorance is the root of your frustration.
Just remember that the next time you get frustrated...