You're Not As Smart As You Think You Are
Cost: My first million dollars
Made my first million by 24. Thought I was a genius. Then I invested in Chinese reverse-merger stocks that turned out to be frauds. Standing in my bathroom mirror, I had to say out loud: 'Glen, buddy... you're not as smart as you think you are.' That was the most expensive sentence I ever spoke. And the most valuable.
The Lesson
Confidence is great. Overconfidence will clean out your bank account while you're busy congratulating yourself.
The Silver Lining
It made me humble enough to actually learn. Everything good in my career started from that bathroom mirror moment.