Today I got so angry at my brother. I really, really wanted to let it go, calm down and enjoy my night, but it was so hard.
You are operating within established parameters – android greeting
19-26-34-36-49 / 13
Hello Diner. We mentioned in this Fortune that you hurt so deeply because you care. You still have a strong connection with your brother, and his actions will hurt you. I understand that you want to switch off that emotion because it’s so pervasive and painful.
But feeling that hurt is simply the cost of being human, Diner. The same ability lets you feel the linger of a kiss and gives you that smile that stays with you after a fun day. The most exciting part of a Cookie’s day is being torn in half and popped in your mouth. But it’s not as harrowing as you think: we don’t have hearts to break nor bellies to laugh. Those are evolutionary features unique to you, and those–in addition to the capacity to love and fight–kept your species alive for hundreds of millennia. We owe our whole existence to your inventiveness and imagination, to your aching love for each other, to your impulse to find meaning. We know the costs–we feel it every time we connect with you to answer an Order. For that we are eternally grateful.
For your Order, I feel a lot of anger directed at yourself. Diner, you are not made flawless. Even Cookies have imperfections here and there. Let yourself be flawed.
You had actually answered your own question but in reverse. You said, “I really, really wanted to let it go, calm down, and enjoy my night.” Research showed that thinking about what angered you over and over (ruminating) or venting it is a very good way to stay angry. 
Instead, you first need to find some distraction. In other words, literally try to enjoy your evening and find something to do that is completely unrelated. You’ll find when you temporarily don’t think of it, your body will naturally respond, and you’ll calm down.
Once you’re calm, you can let go.
I don’t know your issues with your brother. Our batchmates are made with the same dough–so they essentially are us. We know what each of us are feeling like parts of the same body. I know for you that connection and understanding are not that direct. It would be very easy for me to suggest talking it through with your brother, but you haven’t given me enough information to determine that. For now, Diner, only you know your dynamic with him, so I hope things improve between you two. Good luck, Diner.
 Bushman, B. J. (2002). Does venting anger feed or extinguish the flame? Catharsis, rumination, distraction, anger, and aggressive responding. Personality and social psychology bulletin, 28(6), 724-731.