Usually occurs when out partying/clubbing, and most commonly when using the toilet, as the environment is mostly devoid of any stimulation and allows the person in question to self-reflect and fully comprehend how drunk they really are. May also happen when sitting alone for a period of time.
Note for guys: a moment of clarity may be unlikely if using a urinal/trough due to fight or flight response which may distract you from any quiet self-reflection.
This "moment of clarity" is usually accompanied by other strange thoughts including: admiration of the design of the toilet, wall paper, graffiti. Also looking at yourself in the mirror and realizing u look like drunk but you don't care because the feeling of accomplishment for being so drunk and knowing it overrides that.
Guy 1: "Hey dude its been a pretty fun night hey?"
Guy 2: "Holy shit man, I'm having a moment of clarity?"
Guy 1: "Haha yeah you did look pretty pissed on the dance floor the way you groped that chick!"
Guy 2: "Haha awesome! This is the best night ever!! I love you man!"