Do you feel tired all the time? Well, you will be glad to hear that you're not alone. In a recent survey students said that they were too tired. Do not worry though. Help is at hand. Here are some facts about what can make you feel tired, and what you can do to avoid it. You may think that lying in bed until 12 o'clock on the weekend is good for you, but you are wrong. Your biological clock tells you when you are tired. It also tells you when to wake up, and if you upset this by sleeping late on the weekend, it gets confused and you feel even more tired. A particular chemical is responsible for waking you up. It starts to work from 3 or 4 a.m. until 11 a.m. If you sleep any later than this, you prevent the chemical from working, which in turn prevents you from feeling wide awake. You may wonder what being thirsty has to do with being tired, but when you exercise or play a sport, it is very important to drink fluids. You feel thirsty