Up until my 40s, I had a drinking cut-off: 2am. Whatever I was doing, I had to quit at 2am in order to get at least 5 hours of sleep before having to get up for work the next day.
In the past year or so, though, the cut-off time has somehow migrated to... 10pm!! (OK, as I write this, it's 11:30pm, but this is an exception.)
Nothing set, but there ARE internal guides: 10 years ago, I could, indeed, drink all night and get only 5 hours of sleep before work the next day.
Today, though, at 51... I CAN stay up late drinking, but... there's no way in hell I can then get up at 7am for work after only 5 hours of sleep. Nor am I going to have a pleasant day on the weekend after waking up with a huge hangover. After several years of dismissing weekends, because I had no friends to do anything with, I'm just now starting to understand the potential niceness of weekends. (Kind of like the only time I've had Valium: I got my wisdom teeth out back in '87 or something. When the dentist shot me up with Valium, I suddenly felt incredibly calm and good ... "Wow! Is this how everyone else has been feeling all the time?")
I am quite aware that I've been incredibly bereft, sans any love whatsoever, for a very, very, very long time--since age 8 or so? No one else feels bad for me; I now give myself permission to feel very, very, very bad for me.