Have you noticed a difference in your mood and energy levels (your personality for the day) on a sunny day vs. on a gloomy day? Do you notice that in the morning, as the level of sunlight on Earth increases, so does our level of alertness (better known as: it’s easier to wake up when it is bright outside than when it is still dark regardless of how many hours of sleep you had last night). And the opposite, as the level of sunlight decreases, our melatonin levels increase until eventually we put down our devices and go to bed. And lastly, do you know that low exposure to sunlight leads to depression because low levels of vitamin D have an impact on the thyroid gland (the master gland that regulates pretty much every metabolic process in our body).