The average adult only gets three night’s good sleep a week, research from the Mental Health Foundation found. But what is good sleep to begin with, and how can we improve ours? AdvertisementWhat is “good sleep” anyway? The two most common sleep mistakes Dr Bostock sees are from “either ends of the ‘sleep worry’ spectrum,” she said. Luckily, Dr Bostock said that getting better sleep is usually easier than most of us imagine.