You probably won't experience very many all-night parties before noticing this phenomenon. Just before
dawn, when the sky is barely lit and the stars are only beginning to get lost in the noise, people start to disappear. Often this happens despite the presence of good
conversation, a warm fire, excellent music, sundry
booze or drugs, etc. Most ignore these things, instead choosing to go home, crash on a couch, find their
tent, or whatever other form of leaving the party is appropriate. Simply to avoid dealing with a
sunrise.
It's as though they see the sun as an enemy, a big angry orange ball that appears over the horizon for the express purpose of ruining their good time. There's this almost universal notion that once the sun has come up, you should go to bed and feel guilty about your hedonism, rather than enjoying your body's last reserves of energy. One friend describes himself as a vampire in this context, and accordingly takes every step he can to avoid being caught awake after dawn. Often this compulsion leads to steps as drastic as leaving a good party at 3 am, far before it's over and often while it is most fun. Others are less uptight than that, but all share a few symptoms of the fear.
I believe differently. Instead of feeling guilty when the first rays of direct light scatter through the sky, I choose to feel liberated. Sure it's "wasting" an entire night and most of the next day it will take to recover, but there are advantages too. For one, I get the memory of an evening enjoyed for as long as I choose to enjoy it, rather than the blank slate of a night's sleep interrupted with a loud alarm. Also, I share the sentiment that sunrises are best when earned -- that is, little approaches the beauty of seeing a day begin after you've been waiting for it all night.