Light plays a vital role in regulating your sleep-wake cycle. Your body has a natural clock—your circadian rhythm—that it calibrates using sunlight: When it’s light outside, your clock tells you to wake up; when it’s dark, it tells you to sleep.
Not surprisingly, a life spent indoors and away from natural light can push that mechanism out of alignment, making it hard to get to sleep when you need to. Exposure to daylight in the morning suppresses melatonin, your sleep hormone, helping you to feel more awake and energized.
To put your body clock back on schedule, try to expose yourself to bright light during the day—either by going outside or, if that’s not possible, investing in a bright artificial light designed for that purpose.