Because I am not a weight lifter or an Olympic sharpshooter, nothing much happens in my life that demands complete muscular control.
Except sitting in a dentist's chair. Half an hour in a dentist's chair makes me as stiff as a board from controlling all those shouting, kicking, screaming muscles.
Last time I went to the dentist the charming young fellow asked me to raise an arm if the pain got too much to bear.
When his mouth mirror touched my bottom lip my left leg involuntarily did a grand final drop kick and I hit his lamp stand and drink fountain.
I just couldn't help it. The whole thing was an electro-convulsive reaction, a bit like meeting a Trump voter or a climate change denier face-to-face.
But honestly, the anticipation of tortuous pain was just too much. I always try to be polite and do as I'm told when I'm in the grip of professionals. Lawyers, doctors and real estate agents - they all require iron self-discipline not to give in to the easy option of strangulation.
But this was completely out of my control.
Looking back, I think the drop kick was a subconscious laying down of the ground rules.
I was saying - this is my fear and pain threshold.
I'm not a boxer, or a lion tamer or a self-flagellating British Prime Minister. I'm just a scribbler with a very active imagination.
So I apologised, and promised next time I'll raise a hand. The man with the face mask nodded and started again. But I did detect a slight nervous twitch which wasn't there before.
Sometimes I think when teeth were handed out by the great molar in the sky I was at the back of the queue chewing ice cream.
One of my earliest childhood memories is receiving nitrous oxide via a black mask over the face.
I can still smell the rubber. Dentists in those days didn't go in for any nonsense like gentle reassurance and injections. Just gas and pliers. Afterwards, you got a boiled lolly if you didn't cry. Now I think the lolly was building future business.
Anyway, this week I had two crown replacements - each on either side of my face. When I got home my head felt like a football. As the anaesthetic wore off it felt like a football at the end of a grudge grand final.
But looking back, I must congratulate the dentist and his assistant. There was no pain, no torture, no more terror after the first touch.
He was a chatty fellow who said he also played guitar and his nurse stroked my shoulder to stop the tears.
Afterwards, I stood at the counter and got the bill. Suddenly the pain was real. Very real.
20°C