The amount of sleep that a healthy individual needs is largely determined by two factors: genetics and age. Genetics plays a role in both the amount of sleep a person needs, as well as his or her preference for waking up early (these are the so-called "larks," or morning-type individuals) or staying up late (these are the "owls," or evening-type people). Our internal biological clock, which regulates the cycling of many functions including the sleep/wake cycle, can vary slightly from individual to individual. Although our internal clock is set to approximately 24 hours, if your clock runs faster than 24 hours, you tend to be a "lark" and wake up early; if your clock runs more slowly, you tend to be an "owl" and go to bed later.
Give yourself some dedicated wind-down time. It doesn’t have to be a full hour or an elaborate routine, but try to spend at least 20 to 30 minutes doing something that relaxes you before you try to fall asleep. That could be taking a warm bath or shower, changing into comfy pajamas and sipping a cup of chamomile tea. Or something completely different — so long as it’s relaxing to you.