By the time you're in your early 30's you see the same patterns over and over and you go about figuring out why your monkey mind is constantly sending you down a road that isn't working. In your 40's you are conquering your emotions and controlling your impulses.
Anxiety is the root of the problem I see with most people. In our hyper visual world we are exposed to too many things that are unnecessary causing people to desire what others have. This has lead to people in mass having depression because they are attached to what they think will bring them happiness. Attachment and clinging combined with fear are responsible for the bulk of human misery.
It's pretty simple. Most people would think medical doctors are some of the most content people on the planet, they have great careers, well educated, make good money, are respected. And yet that profession has a high suicide rate. I know when I worked in healthcare I worked with 6 doctors that took their own lives in a span of 25 years. This tells me that no matter rich or poor there is misery and the only way to deal with it is to sit down and look for what truly brings peace to your mind.
You're not gonna find it from a relationship or a conquest, achievement, or goal setting. Eventually you're gonna have to step off the hamster wheel and ask "is this really it" and yes this is it. You are no longer spinning your wheels, you now have to deal with the hard stuff, learning to control your emotions, desires, learning to be comfortable with silence, no longer looking for that thing that doesn't exist. Our early ancestors thousands of years ago could be happy just sitting on a log eating a freshly cooked fish in the moment and that is what out biology is built for, not this modern rapid lifestyle that is all about titillating your senses.
If you're interested and have time there is a guy that has a youtube channel "meta sage" that has basically worked through all the bullshit of life and come out the other side. I've worked through this myself with lots of philosophy and thousands of hours of meditation. I no longer give a shit about what happens in life and that's a good thing, not a bad thing contrary to what most people will tell you. Once the attachments are gone, you sleep like a baby.
Meta Sage going to work.