It has become clear to me that, for whatever reason, I can't take much of a punch. This became very clear when I last tried my hand at MMA, and one solid overhand left punched the common sense clear out of me. I notice it in sparring as well, where there seem to be a disproportionate number of blows which buckle my knees.
So how exactly do I correct this? Strengthen neck muscles? Spar with heavy handed guys? Iron Face Qigong?