I am in the opposite situation. Always studied a lot, never really partied during my 20s or 30s. Never really had a long term girlfriend, only short term relationships. Now I regret some of these choices as I am alone most of the time. Managed to stay debt free all my life, made good money but give away quite a lot of charity work. Now being in my 40s, childless and alone, it sucks sometimes.
Your post almost makes it sound like you feel you have wasted time in some way.
Were they choices or were they just your natural self being you? In your 40s, have you turned into a party animal? As far as I'm aware, there's no cut-off age for being a partier. So the chances are good that the reason you didn't party in your earlier decades was that it didn't come naturally. If that's not true, well then get out there and go wild!
For years, I've felt like I'm on the outside looking in - not a partier, value intellectual rather than physical pursuits, etc. I'm alone, but definitely not lonely. The media, OTOH, seems to reinforce that unless you're at a party with a cold beer in your hands every night of the week, you are some kind of loser.
I would venture a guess that most of us were not partiers and I also suspect that quite a few of us lived/live vicariously through those we perceive as wild and crazy people, be they real or fictional.
If you feel being childless and alone sucks, then don't be. There are lots and lots of single people out there, with and without kids.
Or.... learn to appreciate the unique opportunity you have. Complete freedom to do what you want, when you want, and with no claims on your funds except for what you choose to spend them on. That would trump any amount of suckage, IMHO.