I have just gone out to lunch at a Japanese place round the corner from work. I used to be a dab hand with chopsticks but today could not co-ordinate my arm from my elbow

When did that happen - once you know how to ride a bike you can always ride a bike , once you learn how to swim you will always be able to swim - how on earth can you lose a 'skill' that previously you were most accomplished in

P.S I wasn't having an epileptic fit or any other such occurence during lunch