My biggest mistake? Turning down a $2,000 / mo SEO client. How did this turn out posivitely? A few weeks later I found out that he was a fraud and he tends to chargeback monies. While he would have had a big battle to chargeback from me, I still believe that this actually saved a lot of time and nerves on my end.
I just wanted to say this: if your gut feeling tells you something is wrong, it usually is. That guy seemed dodgy from the start anyway but you know, money moves world.
What is your biggest mistake that turned out positively?