Insomnia is when you can't fall asleep or stay asleep at night, which means you don't get a good night's sleep. And it's a very common problem that makes you tired, cranky, and unable to do much during the day. Serious health problems can even be caused by chronic sleeplessness. Don't drink too much caffeine or booze, and don't smoke. Don't eat or drink a lot right before bed. Make your bedroom...