Realizing that the ideal of constant happiness is unattainable. The drive to be constantly happy is causing such misery. No one can be happy all the time, and it is unnatural to think we can be. Contented is OK. Melancholic at times is normal. Happiness, and joy especially, is a rare gift. Accepting that makes a person more resilient because expectations are more aligned with reality.
Compounding interest. Get started while you're really young.
1. Common Sense. Every week I see examples of the pure lack of common sense in life. Companies pay a lot for people who can steady the ship and sort priorities based on common sense.
2. Don't argue over every little thing. We live in such a polarised society and for the most part the answer is usually somewhere in the middle. The amount of people that are willing to die on the hill of something minor is ridiculous so pick your battles.
Exercise
Marcus Aurelius - meditations. He gave us the answers on how to live our lives 2000 years ago but we choose to ignore and continue to make the mistakes that our ancestors did.
Care. If you care about your work, your family, your friends, and put forth an honest effort to support them as well as you can, you almost always come out ahead.
Showing up on time
So much of life is just being there.
Dual income, no kids.
It's only a problem if you make it a problem.