The distinguishing characteristic of being human, is our ability to project experiences into the future. As Dan Gilbert put it, you don't need to try liver-and-onion ice cream to say "YUCK!"
Basically, we can take current and past experiences, and use them to make a judgment on how some stipulated condition will feel.
In the same way, after you've downed 3 bottles of beer and starting to feel the buzz, you know what it would be like if you downed another 3 more bottles. Logically speaking, you'd know when you need to back off. to avoid getting totally wasted.
The ubiquitous drunkenness proves otherwise...