1. The best way to learn anything is to teach it.
The first time I taught chess to a beginner, I learned so much more than he did.
2. Don't worry about the competition.
When I started out as a pro-gamer, the top players in the world were ten times better than me.
3. Do what you love and success will follow.
It's not true but it feels good to say it and maybe it will inspire someone else to do what they love even if they think they won't succeed.
4. You have to fail 1000 times before you can succeed once.
This is good advice for kids who are afraid of failing at something and wants to be successful right away.
5. Know when to quit.
There's nothing worse than someone who wastes their life trying one more time at something that has long since passed them by.
6. Read biographies of people who are better than you in the area you want to be better in.
Knowledge gained from reading is worth 10,000 times more than knowledge gained from experience (unless you are learning a skill like chess or poker where experience is everything).
7. If you want money, start a business that solves problems for people instead of selling useless products or services that don't solve any problems for anyone.
I know this isn't always possible but many "successful" people made their money by selling products or services that did not really solve any problems for customers but they convinced customers otherwise because they are great marketers (which I am not).