These knocks to the head can cause symptoms. I have learned what this is and how to get on with life with them.

Your brain is trying to heal, and bumps that previous to your brain injury would not cause any significant issues can because your brain is more vulnerable.

Knowledge can be a double-edged sword.

I've personally found when I eat clean, do treatments that help my brain heal, my brain is more resilient and bumps phase me little or not at all. And vis versa. When I lose discipline, my brain is more vulnerable and I function worse overall.

I believe this may be due to a number of physiological effects:

inflammation
oxidative stress
the brain's overall connectivity being scrambled ("cellular tensegrity" is a more scienctific phrase)
imbalanced (lack of or too much) blood flow, oxygen, and other nutrients
dormant neurons
potential neurotoxins (heavy metals, endotoxins, bacterial, fungal, parasitic, and/or viral)

That's the body based side of things.

The mind is huge in controlling the response of the body post head hit. I used to be terribly, terribly anxious because my brain was physically super sensitive to these bumps. Over time, with lots of work on healing my brain and it becoming less sensitive, I learned not to focus on my symptoms especially in response to these bumps. Cognitve Behavioral Therapy - control your response by regulating your nervous system. Breathing is huge for me. If you breathe calm, your thoughts calm. If you breathe stressful, your thoughts and body gets stressed and you are no longer in a healing state.

In sum, the brain takes time to heal. To speed up the process, do things that heal it. Your brain needs care and nurturing. But keep in mind, that the brain can heal amazingly well given the right support.

I also see your profile name. I also play guitar. Great instrument.