Maybe it's just my perception, but I think people feel like that when they're fulfilling other people's ideas of what they should do with their lives.
They get the job that people think they should have - something basically respectable that uses your brain just enough but doesn't stray too far into the realms of creativity and doesn't take you away from your kids for too long.
They marry the guy that seems like a safe enough bet - same class, same race, similar job etc, basically attractive, basically socially acceptable etc.
They have kids because they hit 30 and everyone else is having kids so they think they should have kids too.
They buy a house because that's what you do, even if it means you stress about it for ever more.
It's so so so easy to be pushed along and do everything in the right order school university job marry kids die. And I'm not criticising anyone for it, but I do think that if you're not happy with your life, you definitely have the power to change it, even if you do something totally ridiculous like quit your job with no safety net or move to Mongolia or retrain to be a dog yoga instructor or whatever. I mean, if you're miserable anyway, then why not just change stuff?
A lot of my friends have told me I'm lucky because I moved to Korea spur of the moment and now I live here. But like, I'm not lucky, I just did it. They have the same qualifications as me, there's no reason they can't do the same, but they worry about their career and what their family would think etc. I just can't live my life like that, worrying about 'what if this happens'.
I've been in pretty disastourous situations (no money, no friends, no job etc) various times, but I've never been bored.
Like I said, no judging or criticising, but if you have a roof over your head and enough money for a meal then you have a million more ways in which you can change your life than 90% of people in the world, so why spend your life feeling shit and never changing?