As someone who is in their 20s and got an early start, FIRE and frugality aren't the bummer that some are making it out to be.
I don't feel deprived of anything, I feel optimized. Maybe that's because I make a pretty decent living, but given that OP amassed a million by their forties without finding FIRE communities, I'd say the same probably goes for them.
It's not about depriving myself from going out with friends. It's the recognition that the, *ahem*, "character building" of a shot of well whiskey is just as much fun as an $11 shooter.
It's not about depriving myself from eating out. It's the recognition that leaving the office and driving a few miles to spend $10 on lunch doesn't bring me much joy, and that learning to prep my own work lunches is cheaper and healthier anyway. I still go out to eat with my girlfriend about once a week, and more if it ends up as an excuse to see friends.
It's not about depriving myself of travel. It's the recognition that a little bit of time and effort working rewards programs, and sucking it up and going with discount airlines and flexible travel means that I travel more than I ever thought I would. Two hours into my destination, I'm not thinking about how much Spirit sucks, I can tell you that.
I do totally agree that a life without regret is the best one to lead though. And everyone has to do what makes them happy.