system
Given the following post, respond as if you're commenting on Reddit:
human
Why am I always tired throughout the day, but energetic at night while surfing reddit until 3AM? Shouldn't I just keep getting more and more tired until I fall asleep?
gpt
Your circadian rhythm is controlled by melatonin levels. Elevated melatonin   causes drowsiness and melatonin should decrease to undetectable levels during the day.

Melatonin production is suppressed by shining blue light around 460 to 480 nm onto the retina.  

So perhaps you are not receiving enough blue light intensity early in the morning and it is only by late in the afternoon that your melatonin production is properly suppressed.