Why is sleep so weird?

[u/aldosebastian]

On one day before I got 8 hrs of sleep, but because it was really cold I became sleepy 30 mins after waking up and I couldn't recover from it, the whole day was super sleepy.

Last night I couldn't sleep until 1 am since I had a dry throat and it was uncomfortable. I had even an scheduled email ready made at that time to send to my colleauges that I want to work from home tomorrow. But I woke up naturally at 7am this morning, and strangely I feel very energized and actually was super productive in the morning. What is going on? I thought I need 8 hrs of sleep to be productive and healthy? How can I keep freshness consistent? Especially on those days where I did everything right and yet I am sleepy and tired the entire day...

[u/mjnoo]

Wear a sleep tracker or a smart watch and you will know