The act of wishing you were at a bar imbibing in libations when in actuality you're forced to do something mundane and extremely adult like go to work, show up for court, do laundry, etc.

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.

The act of timing your heavy drinking with the arrival of a drug dealer so you don't blackout before their arrival and delivery of your nose beers.