The only way to truly re-wire your dog's brain involves activating old memories and then re-configuring them. This means that if you shelter your dog in a bubble of "safety" and always DISTRACT them from triggers, you may be successful at keeping them under threshold... but the underlying emotions and reactivity programs in your dogs brain are not changing.
Of course, it does help to initially interrupt the rehearsal of reactive and aggressive behaviors. But eventually, you must TRIGGER the dog and then re-pattern their behavior with careful titration and training. When old memories are activated, you have the opportunity to add new information!
Then you want to give your dog plenty of rest so the brain has a chance to integrate the new information. This can be a long and tedious process, as the brain doesn't want to erase or let go of fear memories. The brain is meant to promote survival, and this is why people always talk about the "negativity bias."
The other point to realize is that you can't just teach your dog to be calm in the face of triggers. You must use the arousal energy that your dog is experiencing to now shape something positive, empowering, and fun! Anxiety and excitement are responsible for releasing the same neurochemicals and creating the same sympathetic nervous system state. So we slowly train your dog's brain to feel excited about expressing their arousal in constructive ways. We channel that arousal into wanted vs. unwanted behaviors.
At the same time, we should be working on your dog's confidence in other contexts, away from triggers. This will not only help develop new neural pathways, but gives them a chance to increase their emotional capacity.
So there has to be a multi-prong approach and it's not always easy to find the correct balance of interrupting unwanted behaviors, shaping new behaviors, resting, and working on confidence building all at the same time! It is critical that your dog is not chronically "stressed" by excitement OR anxiety because both states release cortisol, and constantly elevated cortisol can actually damage the prefrontal cortex.
This is why it's important to consult with a trainer who is experienced in the specific behavioral concerns that you have with your dog.