Back when I was 20 I had a drinking problem. One time I drank so much that I passed out sitting at a table. Woke up with friends having stripped my clothes and washed them. I woke up at 9AM, feeling 100% sober, just anxious about my 20 missed calls from my mom. I got a bit drunk at about 33 and next day I thought I was dying.
That's how I learnt what hangovers were.
Again, at around 25, I helped my brother in-law move bee hives all night, including some 8 hours of driving.
Went straight to work and in the evening I had dinner with my wife at a restaurant.
Now I crash in bed at 9PM and if I'm lucky, I also sleep (but quite often I wake up at 2AM).
Getting old(er) sucks, and I'm only 42 and I miss so much how nice being in my 20 something body felt all the time.