People wear helmets for other sports all the time and don't get anxiety attacks from it. The foam lining in these hats is barely noticeable so it's the same as wearing an ordinary hat.

When someone has severely debilitating symptoms from multiple head hits, did they make the mistake of not relaxing enough???

Saying all symptoms are due to anxiety is not helpful because it does not address the underlying causes of concussion symptoms. There is more going on than just anxiety, and people know it. Yes, anxiety may contribute to concussion symptoms, and it may be a roadblock, but it's not the only factor and it's not the main factor.

The bottom line is that you need to protect the head while recovering from a concussion. At the very minimum that means stop participating in risky activities. If you can get through your concussion without banging your head, then great. But if head bumps become a problem, then more protection is needed.