I start "partying" at 5p and in bed by 1030p.
I used to get up at 1030p to go out for midnight-1a.
I am okay with this.
I am so comfortable being more of a home-body - and when we do go out, or have a bbq or visit friends, i'm certainly not pulling all-nighters.
I remember when i used to *love* watching the sun come up after a big night on whatever drug i'd taken the night before - and while my love of sunrise has only grown over the years, i'm appreciating it far more these days when it's the beginning of my day, not the end.
I look back so fondly on my partying days; I had an absolute ball... but i would never want to go back to that. I do get twinges of "oh i remember this!" shivers when i listen to music from my salad days, or if I talk to people i partied with, but never *truly* feel nostalgia (although i do use it as a bit of a throwaway word). I never yearn for the days gone by. Hell, the clubs i frequented in my early 20s are still there, but are still frequented by people in their early 20s. I'm pretty sure one of the clubs is caught in some kind of time rip lol.
To MDAO - The only thing I can suggest is to hit the local media to see what's going on in your city; head out and explore. I have found that it's on these occasions I find the most interesting things. You may be pleasantly surprised. I always love being a tourist in my own city. Grab a couple of friends and make your own adventure.

In my experience, the more you immerse yourself in things that are new to you, the less you look back with yearning.