Viewing bright sunlight within the first 30 to 60 minutes after waking triggers a cortisol increase, which is essential for alertness and focus throughout the day.

Viewing bright light early in the day helps synchronize the cortisol pulse, providing energy and focus for the day.

Cortisol spikes in the morning are beneficial as they help wake us up and have important health-promoting functions, while a 9 PM cortisol spike is a signature of depression and anxiety, which is problematic and associated with many mental health issues.

If you don't view light early in the day, the cortisol pulse can shift later, leading to mood issues and sleep problems.

The rise in body temperature after your temperature minimum triggers cortisol release, which helps wake you up and enhances focus.

Using red light in the hours before needing to be awake can help maintain your normal cortisol rhythm without disrupting sleep.

Bright lights at night suppress melatonin, the hormone responsible for sleepiness, and increase cortisol levels. Blocking short wavelengths of light can help mitigate these effects.

Engaging in activities like sunlight exposure, physical exercise, and cold exposure in the first phase of the day can enhance your alertness and focus, making it easier to adopt new habits.

Using tools like morning sunlight, exercise, and proper timing of food intake can help set a predictable circadian rhythm for better sleep, while during the middle of the day, limiting caffeine intake and being mindful of the clock-delaying effects of exercise can optimize your sleep.