You're not going to control any emotions in a fight usually, unless there's time to prepare or it's playing out for quite a long time. What you can do is learn how to fight with aggression and overwhelming violence and how to work n critical thinking when emotions are clouding your normal thought processes. These are the things that help you prevail in a fight of any kind.
I know a few people on this forum hate this word, but training is how we learn to do this. Not at an indoor range on our own, but by attending classes that focus on mindset and problem solving. Learning to think clearly when all else is blowing up around us is something we should be working on.
Explain to the jury how you shot the BG because you were angry. Then explain how you shot the BG because you were in fear. See which argument sways them best in your favor. Use whichever emotion works best for you, but keep it to yourself.