Can't beat the sleepiness

In Japan, there is this saying "In spring one sleeps a sleep that knows no dawn".
It's originally Chinese and is a sentence from one of the Chinese poems called kanshi.
What it fundamentally means is that the sleep in spring is so comfortable that you never realize the break of dawn, and in my reality... so drowsy that I can barely keep my eyelids open.

Even when I sit towards my desk, each movement becomes super slow. First, my brain stops functioning and abandons to "think". And then from the fingers I set on the keyboard I get this sensation like my blood is flowing backwards, but still I feel so relaxing, and then that sensation spreads across my body to my head and to my legs.
Slowly any kind of sound around me starts to fade away like I got my ears muffled, then my body grows warm from inside, and by the time that warmness reaches my ears my mind is already off to the world of dreams.
And you know, at times like this you never realize that your eyelids had shut, so without being able to be aware that you're actually sleeping, time passes surprisingly fast. So when I see the clock again, I'm always like, "Hey, was I sleeping?"

Well, I'm not too different the rest of the year so it doesn't sound that...uh, you know.
But even then, why is it that you get so easily sleepy and tired in spring as people have been saying for thousands of years ago?

A recent study reports that this spring drowsiness has something to do with the disturbance in the balance of the autonomic nerve, which supposedly keeps control of various functions like breathing, digesting, circulation and metabolism.

During winter, this autonomic nerve controls the blood veins to tighten up so that no extra body heat goes out of the body. But in spring when the weather becomes warmer, the nerve orders the veins to loosen to let body heat out. The thing is that during this season shift, weather and temperature fluctuate so much from day to day, morning to night that the nerve loses control of adjusting and becomes very unstable. And when the autonomic nerve is disturbed like this, uncomfortable symptoms like drowsiness and listlessness start to show up, contributing to the increase of people saying, "I get really sleepy in spring."

Scientific researches like this really helps me you know, cuz I can make an excuse by saying "sorry, my automatic nerve seems to have lost balance" when I fall asleep during work. Hehe, just kidding.

Anyway, anyone out there coming to Japan on say a business trip, don't be upset when your business partner seems sleepy and unconcentrated. Sleepiness disturbs carefulness and discretion. Perhaps leaving your partner sleepy would be favorable to you, lol.