That happened to Ryan* when out-of-the-blue two years ago, aged 52, he developed a form of epilepsy. He was employed as a security guard and, with the best will in the world, people who have recurrent seizures can't hold onto that kind of job. Of course, he could no longer drive either and because in the UK we have to be seizure-free for one year before the DVLA reissues a licence, he's still not driving.
"I thought my life had come to an end!" he says. "Everything I knew was taken away from me."
That seems a bit dramatic to me (and I've told him so - but, then again, I was a teenager when I was diagnosed so have lived a pretty epi-ful life and had plenty of time to get used to it. Yep, in some ways I've had it easier by having it longer!)
He says: "I kept telling the professor he couldn't be right when he diagnosed 'epilepsy'. I told him I didn't fall on the floor and shake. I didn't believe him - and I didn't want to believe him. I thought my life would be over."
*Name has been changed to protect identity.