system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do I get tired around 2 or 3 PM despite having gotten enough sleep the previous night?
gpt
It is the second low in a persons daily circadian rhythm.    
Simply, a persons (biological) circadian rhythms (circadian rhythm = hormones, metabolism etc) naturally cycle through highs and lows during a 23.5-24(ish) hour day.    
They have 2 low points with the lowest point occurring at around 3-5 am(ish). This is why accident frequency data (work, driving etc) demonstrates a spike during this time.     
There is also another low at point, albeit not as significant, which occurs at around 15:00.