A friend of mine from high school sent me something in an email that finally provided clarity. I remember reading it at work, and where I was working at the time, so this would have been the late 90's or early 00's.
It basically said that when you're young, you think that "all you have to do" is get a good job, find your wife/husband/soulmate/whatever, find a nice place to live, and you can live happily ever after.
So you work to get through college, or maybe head into the workforce right away. You work, you keep thinking "right now I'm only <something> but once I get to <manager/director/VP> things will really be good."
Your first car may not be great, but it's fine, and someday you'll have a <nicer car> and things will really be good.
You start a family, and yeah having kids is rough, but you think once they're older, things will be easier, things will be good.
It was all stuff like that. If you just keep at it, you'll get to the next plateau, and things will be good. Then at some point you look around and realize you've been working your ass off your entire life so far, and things may not be perfect right now, but half your life is now behind you and you're still waiting for things to be "good". You're still trying to get to the next level, because then things will be good.
Look at what you have now. Look at who you have around you right now. Look at the life you're living right now. Look at the car you drive, the house you live in. You're here! You've arrived. This is your life. Stop waiting for things to be "better" and enjoy what you have right now, because right now will only be here once. Say those things to your kids that you've always meant to tell them. Say those things to your wife/husband/soulmate/whatever that you've always meant to tell them. Do that thing you always wanted to do. This is your chance. This is the life you've built, the life you've earned, and you don't get another shot at it.
Basically "stop and smell the roses". I never really understood that expression until that moment. It really just means to take a second to enjoy what you have now, instead of constantly looking towards the next thing and thinking it will be better. Don't stop trying to improve things, but take the time to enjoy things now.