I have a friend, a female who was also raised on a reservation, and she experienced terrible trauma, including from her own family. Unlike you, she has reacted differently when faced with physical threats. For example, once she became so angry at someone who was abusing her that she 'blacked out' and the next thing she knew she was choking the guy, and would've killed him if she had not 'awakened.'
Second, that was a really low class operation where you sparred with some guy; both the 'school' and the guy should've known better, and basically you have to learn things like that are not your fault. Easy to say, etc. But as the replies above have advised, you have to find people who have first-hand knowledge of 'wisdom in life.'
For example, you mention your mom. She was certainly cool-headed in that encounter in the park. Maybe she can help you find others who can guide you.
Another thing that I've noticed: I volunteer at a program where we prepare lunches for the poor. I happen to be a chef, and others are either assistants, or they serve, or clean up, etc. But the point is that I'm surrounded by wonderful people (and sometimes the friend mentioned above comes and helps too, and that helps her). It may be a cliché, but it's true. The more you give, the more you receive.
Also, it's interesting that sometimes there are some people we serve who become belligerent (not often), and I've had to step in, or others have. So that's great practice. If a person is 'skittish' as you describe yourself, it would be a help for you to observe these dynamics and that things can 1/ quickly be de-escalated or 2/ calmness also quiets down even the most belligerent. In the latter, some guys knew that I would be through being Mr Nice Guy and that I would have no problem with them. And they quieted down just like that. I didn't have to shout or act the bouncer. Especially if you live in a big city, the 'clientele' will be a little rougher than smaller towns. In big cities, I notice they have lots of security.
Anyway, my final point is that you meet in your life what is inside, so you have to look for that 'calm' that is inside you. Again, if you surround yourself with positive, strong people, this will have a big impact. Oh, another illustration, look up HeartMath.org. they have proven the power and value of thoughts/emotions. A human has a magnetic field at least 10 feet from body, and this is 'felt' by others, although usually subconsciously. Scientists venture that actually just that one field alone extends hundreds of feet, we just don't have the instruments to detect them, yet. The heart has a field that's 5,000 times stronger than the brain! So you can see the power of emotions. Hope this is of some help. Finally, the true martial art teaches us never to give up. Never give up. My friend has never given up, and she has experienced some very bad stuff that would knock out the Hulk. Think of that. There is also something strong in you that keeps you going.
