阅读理解 Your habits－both what you do and what you think－can cause many sleep problems．Here are four ways to help you sleep better． Establish a sleep schedule． Your body's internal timekeepers want you to get up at the same time every day, including the weekends, which is probably the most important step toward establishing good sleep patterns, because regular exposure to light in the morning is what sets the brain's alarm clock．You can mark your inner clock's point more clearly in the morning by taking a walk or by having breakfast beside a sunny window． Regulate your body heat． Even small ups and downs in body temperature play a large role in your biological rhythms．Sleep generally follows cooling state of the body's temperature cycle．One way to control body temperature is with exercise．A workout lasting 20 minutes before before bedtime may encourage sleep．Too much exercise：two or three hours before bedtime, however, can keep you awake．You might also try a hot bath well before bedtime, which can help influence body temperature． Skip caffeine－even in mid afternoon． Research suggests that the caffeine from three cups of coffee still has effects up to eight hours later．Some people are more sensitive to caffeine than others．Some are also more affected than they realized．Research subjects who say they can drink coffee before bed and sleep well actually don't sleep as well as they think when you test them in lab．Remember, too, that other substances－chocolate, cola and tea can cause poor quality rest． Avoid nightcaps(睡前饮料)． Yes, alcohol does help you fall asleep．But as it's metabolized(代谢)by the body, it releases a natural stimulate(刺激物)that disrupts sleep during the second half of the night．And the greater the quantity of alcohol consumed, the worse the disruption． | 
