When i see a client I ask a series of questions, how has your week been? Did you eat right? How is work going, how's your stress level? Did you work out this week? Lastly how are you sleeping?
Sleep is without a doubt the one thing that our bodies need but we think we can get by with less. An adult should be getting 7-8 hrs. a night. What do you think you're actually getting?
Kids are probably the worst offenders. A teenager who is still growing and developing need 10-12 hrs. a night but probably get half that.
Take a look at this link that goes into much greater depth about the importance of sleep.