That's how you know it's all over. I'm old now 
SLEEPY OR NOT I'LL DRINK WADDDUPPP.
But yeah I know it. But I ignore the sleepiness and pour me another one..
Drinking when you're sleepy is kind of a waste, because you're not there long to enjoy the alcohol, you'd most likely just doze of in 30 minutes.
Not saying you should Wake up and DRINK.. but ... probably some time in the afternoon after a nap.
//Yes Tp4 = old too.