I have two sisters, and out of the three of us, none of us sleeps well. My younger sister cannot drift off, and keeps a pile of books by her bed with which she reads herself to sleep. I crash out, no problem, only to wake between two and four in the morning, when I may get up and work for a couple of hours before returning to bed and falling into such a deep sleep that, when the alarm pull me into consciousness at 7 am, I feel as if I have been hit on the head with a hammer, My twin sister, meanwhile, has no need of an alarm: her own personal one rings at about 4 am, whereupon she tosses and turns for an hour or two until she finally gives in and gets up.