Your sleep is regulated by daily cycles of hormones called circadian rhythms. These cycles are your body’s “internal clock” and regulate sleep, alertness, body temperature, and metabolism. That clock may cause you to wake up at the same time every day. Body rhythms are also affected by external factors, primarily light. If you’re exposed to light in the morning, it will trigger wakefulness, no matter what time you fall asleep. Wearing an eye mask or using blackout blinds may help you sleep later.