Anger implies a harsh reaction, one in which we experience animosity or other very negative reactions. This is completely inappropriate if we understand that what is happening to us has meaning that we perhaps don’t see or don’t understand. There is a huge difference between feeling confused or frustrated and being angry. Anger also implies that we are angry with another person. This would mean that someone else is responsible for the outcome or the cause of our dissatisfaction. However, when recognizing that the other does not determine what happens, but that G-d controls this world, then anger is really an escape from the real work, which is figuring out what can be done in the future for a different and more pleasing end result.

Also see Why is anger—a seemingly natural feeling—so anathema in the eyes of G-d??