Our internal clock or biological clock, as we say, is synchronized well with the rising and setting of the sun. Many of the internal functions and systems of the body work as per the coming and going of natural light. Messing up with this can cause a lot of harmful effects on our mind and body. That is why people who work at night and sleep during the day have a weaker immune system and are more prone to diseases as they suppress their biological clock and do not follow a natural rhythm.
Circadian rhythm is basically a daily cycle that everybody tends to follow, including sleeping, eating, and mating. There are specific points in the day when you feel sleepy and at certain times when you feel hungry. That is your circadian rhythm. Natural light causes our heart rate and blood pressure to rise while suppressing the release of hormones like melatonin. Thus, helping us wake up and stay active throughout the day. Following our biological clock helps strengthen our immune system and keeps us healthy. It makes us more alert and our mind more active.