I allowed my family to talk me into getting it all chopped off to 2 inches (actually, I was simply tired of the pressure therefrom), and, in a Samsonesque turn of events, I subsequently became physically and emotionally weaker.
I've seen this happen to others, and although I'd considered having to fight a slight energy tweak after the chop, I greatly underestimated the power of this phenomenon, at least as it pertained to me in this case.
It's funny to me that I've not had the guts to date a lawnmower since, so it's been 2 years now and I've no desire to return to a hairdresser.

FWIW, my monkey-theory on this subject has always been that the hair acts as a sort of energy dampener and/or aerial.
Experienced hairdressers have noticed (usually only after I've asked them the question!) that as a generalisation, those with longer hair tend to be calmer.