That point for most of us though doesn’t normally occur till we’re at least 40.
I remember exactly when and how this happened to me. It was towards the end of my time at Anglia TV, and I was being photographed in a Father Christmas outfit to advertise a Toy Appeal. (Well, someone has to do these dreadful jobs!) The session went on a while and when I straightened up and handed back the sack of toys I’d been carrying on my shoulder, my back went into a very painful spasm.
Naturally, I got better in a week or so, but from then on, I realised that I needed to treat my back with much more care and consideration – and some 30 years later I still have to.