When I was younger, I was indestructible. Or, at least I thought I was. All through my teens and twenties, I would routinely risk life and limb, cliff diving in Acapulco and driving at the speed of sound the wrong direction up one-way streets – all without a thought to the consequences if something were to go wrong. Old age has changed all that. And, I look that way too. Nowadays, before I even open my eyes in the morning, I run through a comprehensive physical checklist prior to swinging my feet out of bed – lower back: check. Right and left knees: check. Feet and ankles: check. Hands, wrists…