Anger is a departure from your true-self. Unjustified, out of control anger, that is. Justified doesn’t mean creating an excuse. It means there was no better option. Objectively no better option.
Anger will ruin your focus and prevent you from being productive. You have to let go of your anger so you can stay focused on what’s important. Your time is limited, don’t waste it thinking about things you can’t control and which make you feel terrible.
You will have moments of anger and frustration, but you can always come back to your true-self. The main thing, is you don’t allow it to ruin your day or someone else’s day. The key is to get over it quickly, before you cause too much havoc.
There is a legitimate purpose for anger. If someone attacked your child you would get angry, as you probably should. Your child needs you to get angry in such a situation. And there are other times when you need to be angry also. The problem is we get angry too often and we sometimes allow it to cause too much damage.
I think this is the meaning of “be angry and sin not.”