But I noticed there was a big problem: my whole life everyone has been telling me "don't exercise before bed". The reason you shouldn't exercise before bed is because it will get your body excited and ready to move around, and will get your body not wanting to sleep. Even though some people think it's good because it will make your body tired, it will make your arms and legs more tired but it won't make you fall-asleep tired. When I exercise before bed I normally end up wanting to get up and play when I'm trying to fall asleep. I think this is a big problem with this book.