We are vulnerable in sleep as the vampire shift of ops knows all too well. A lot of people go to bed around 11 or 12 and wake up around two or three and can't fall back asleep. One way you can get better at sleeping is to use an app like Revery, REV-E-R-I. There's a sleep function in there that will allow you to try it for free. It teaches you to relax yourself into a state where then you drift off into sleep.