Henry Nicholls has had narcolepsy for half his life. He says the condition is like being sleep deprived and overslept at the same time, and there is no cure. Looking into narcolepsy, he learned about a host of other disorders too, including “sexsomnia,” where people engage in sexual activity when they’re asleep. And there’s the condition many of us have: insomnia. He gives us tips on how to retrain your brain to get better sleep.