Besides that: being too friendly, too accommodating, and too much of a team player when I was younger. That behavior is rarely rewarded. You owe loyalty to yourself, your family, especially your children, your spouse, your lifelong friends, and your dog. Your dog might be the most faithful of these.
Be careful who you marry. A good marriage is worth more than a lottery jackpot; a bad marriage is like a plane crash with yourself in a window seat. Choose very wisely. And don't choose with your dick alone.
Not taking up my friend's crazy invitation to fly halfway around the world for a BBQ, half a year before his diagnosis and rapid death. You only live once. Always live as if you might have only a few months left.
Remind your friends to get their annual health checkups. It may matter more than you think.
"You have two lives: one before you realize that your time is limited, and one after."
"The best time to get in shape was ten years ago. The second best time is today."
"Play stupid games, win stupid prizes."