Got a classmate who had severe concussions from snowboarding feeling some serious consequences now just stopped training based on doctors advice. Not so much because he gets head injuries during bjj, but that according to his doctors, adrenaline is the worse thing for your brain. As for me, I have some bad disc degeneration and bad curvature in my spine and neck. I don't want to quit training, but the thought is now crossing my mind. What about you guys? How bad does it have to get before you hang your gi up for good?