"Either way, I feel if I get hit by an acorn and somehow by luck the following day I am feeling bad, I will end up associating these two together. In other words, it takes courage for someone with concussion to accept that even tiny things will fall on his head from time to time... "

This is irrational thinking. You will benefit greatly if you can get successful help to overcome this issue. Otherwise, living a life of anxiety will be a constant struggle.

It doesn't take courage, it takes sound thinking.