If you get serious, you become the center of localized problem-solving. If people start getting serious en masse, problems start to get solved on a larger scale. Unless the whole human race decides to get serious, all the world's ills will never be solved. So just settle for what's in your power. Perfectionism is futility.
If you're not serious, you won't be able to follow through. If you're not serious, you won't be able to focus. If you're not serious, you will get distracted. If you're not serious, you'll give up too easily. If you're not serious, you'll settle for a half-assed job or sweeping things under the rug.
If you're not serious, you won't respect yourself. And if you don't respect yourself, you won't really respect anything or anyone.
If you're not serious, you'll never be in a position to laugh at absurdity. You have to be serious to have a sense of humor. It's a matter of having a basis of comparison.
Don't get distracted by anybody selling grand overarching solutions, unless he shows signs of moral seriousness. Especially if they're vague and shouted with lots of animated gestures. That's how Marxist-Leninism got started.
I have no grand overarching solutions to offer. I make no apologies for this.
Specific solutions to specific problems will become obvious to a reasonable intelligence. But only if you get serious first.
Think tactically, not just strategically. Be input-driven and adaptable to changing situations. Try to see things coming. Be immune to surprise.
Prioritize.
Every experience is an opportunity to learn. Except death. So don't die unless you have to.
If something works, try it again. If something doesn't work, try something else.
P.S. Read about the Scottish Enlightenment. Those guys were seriously enlightened. They confronted problems, and actually solved a lot of them.