There were times over the last year I would sleep during the day and live during the night. Traveling and having no fixed work schedule messed up my internal clock quite badly and I am now working on getting back to a more regular cycle, meaning a cycle closer to my natural circadian rythm, a sleep/wake cycle of roughly 24 hours coinciding with the daytime/nighttime cycle.
Our energy levels throughout the day are linked to the sun. We can cheat on them using substances such as caffeine or external stimuli such as artificial lights, but it isn't how our bodies are programmed by design. Whether you are a night owl or a morning person, we are animals following a circadian rythm.
Waking up earlier is not just a productivity tip you can read everywhere, it is also more environmental-friendly. Electricity is the second biggest source of CO2 pollution after transportation, and light pollution disrupts both nocturnal and diurnal creatures. Decreasing your dependence on artificial lights makes a lot of sense. Similarly, reducing your exposure to blue lights helps increasing sleep quality, and thus your overall quality of life.
I am fortunate to have no fixed schedule, therefore I am free to rise and fall with the sun. Every late afternoon I check the dawn time and set my alarm clock to wake up half an hour before it (6:28 AM tomorrow). I go to bed whenever I feel tired at night up to eight hours before my wake up time. This way I ensure I get enough sleep.