At 20, you care what everyone is thinking about you. At 40, you don't give a damn what people are thinking about you. At 60, you realize no one is thinking about you.
I recently sent this little missive around to a bunch of friends and their reactions were varied and interesting. Many thought it was funny and even cute, but some were saddened by it. I don't quite get that. To me, it's the best part of getting older. You have a much better sense of reality and are able to deal with the real world far better than you can in your 20s.
In your 20s, you are totally paranoid and know for sure that everyone is smarter than you. Better schools and better grades mean they must be smarter, right? Not so fast. As you gain experience, (a PR word for "age"), you realize that not everyone is smarter than you are about everything. That, in fact, you are smarter than your contemporaries in a certain number of skills—whether it is writing, speaking, street smarts, selling ideas or creating ideas. If you're an entrepreneur, you quickly learn to hire people far smarter than you — because if you're the smartest person in the room, you lose.
Another thing you learn is that life truly is random. You can plan for weeks on end, only to see things change in a heartbeat because of situations that are out of your control. So focus on what you can control and let the rest play out. You'll have a much more enjoyable life, and probably a more successful one as well.