Accept that perfection doesn't exist. Your relationships will have problems, your car will break down, someone else will anyways have a better phone, a newer car, or a bigger house than you, no matter where on the social ladder you stand. Constantly chasing perfection will keep you permanently stressed. That doesn't mean you should not try to better your life, just know that if you expect perfection you will never be statisfied.

Pay attention to your diet and health. I have been working out at least 4 times per week since my mid 20's. I am fitter, healthier and look younger than almost everyone else my age

Don't stop doing the things you love. Even though I have a wife, kids, job etc. I still make time to play video games, draw, write stories, read comics, play basketball, listen to music, etc. There is no reason to become a miserable old bastard!